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  • Tips for XNA WP7 Developers

    - by Michael B. McLaughlin
    There are several things any XNA developer should know/consider when coming to the Windows Phone 7 platform. This post assumes you are familiar with the XNA Framework and with the changes between XNA 3.1 and XNA 4.0. It’s not exhaustive; it’s simply a list of things I’ve gathered over time. I may come back and add to it over time, and I’m happy to add anything anyone else has experienced or learned as well. Display · The screen is either 800x480 or 480x800. · But you aren’t required to use only those resolutions. · The hardware scaler on the phone will scale up from 240x240. · One dimension will be capped at 800 and the other at 480; which depends on your code, but you cannot have, e.g., an 800x600 back buffer – that will be created as 800x480. · The hardware scaler will not normally change aspect ratio, though, so no unintended stretching. · Any dimension (width, height, or both) below 240 will be adjusted to 240 (without any aspect ratio adjustment such that, e.g. 200x240 will be treated as 240x240). · Dimensions below 240 will be honored in terms of calculating whether to use portrait or landscape. · If dimensions are exactly equal or if height is greater than width then game will be in portrait. · If width is greater than height, the game will be in landscape. · Landscape games will automatically flip if the user turns the phone 180°; no code required. · Default landscape is top = left. In other words a user holding a phone who starts a landscape game will see the first image presented so that the “top” of the screen is along the right edge of his/her phone, such that the natural behavior would be to turn the phone 90° so that the top of the phone will be held in the user’s left hand and the bottom would be held in the user’s right hand. · The status bar (where the clock, battery power, etc., are found) is hidden when the Game-derived class sets GraphicsDeviceManager.IsFullScreen = true. It is shown when IsFullScreen = false. The default value is false (i.e. the status bar is shown). · You should have a good reason for hiding the status bar. Users find it helpful to know what time it is, how much charge their battery has left, and whether or not their phone is in service range. This is especially true for casual games that you expect someone to play for a few minutes at a time, e.g. while waiting for some event to start, for a phone call to come in, or for a train, bus, or subway to arrive. · In portrait mode, the status bar occupies 32 pixels of space. This means that a game with a back buffer of 480x800 will be scaled down to occupy approximately 461x768 screen pixels. Setting the back buffer to 480x768 (or some resolution with the same 0.625 aspect ratio) will avoid this scaling. · In landscape mode, the status bar occupies 72 pixels of space. This means that a game with a back buffer of 800x480 will be scaled down to occupy approximately 728x437 screen pixels. Setting the back buffer to 728x480 (or some resolution with the same 1.51666667 aspect ratio) will avoid this scaling. Input · Touch input is scaled with screen size. · So if your back buffer is 600x360, a tap in the bottom right corner will come in as (599,359). You don’t need to do anything special to get this automatic scaling of touch behavior. · If you do not use full area of the screen, any touch input outside the area you use will still register as a touch input. For example, if you set a portrait resolution of 240x240, it would be scaled up to occupy a 480x480 area, centered in the screen. If you touch anywhere above this area, you will get a touch input of (X,0) where X is a number from 0 to 239 (in accordance with your 240 pixel wide back buffer). Any touch below this area will give a touch input of (X,239). · If you keep the status bar visible, touches within its area will not be passed to your game. · In general, a screen measurement is the diagonal. So a 3.5” screen is 3.5” long from the bottom right corner to the top left corner. With an aspect ratio of 0.6 (480/800 = 0.6), this means that a phone with a 3.5” screen is only approximately 1.8” wide by 3” tall. So there are approximately 267 pixels in an inch on a 3.5” screen. · Again, this time in metric! 3.5 inches is approximately 8.89 cm. So an 8.89 cm screen is 8.89 cm long from the bottom right corner to the top left corner. With an aspect ratio of 0.6, this means that a phone with an 8.89 cm screen is only approximately 4.57 cm wide by 7.62 cm tall. So there are approximately 105 pixels in a centimeter on an 8.89 cm screen. · Think about the size of your finger tip. If you do not have large hands, think about the size of the fingertip of someone with large hands. Consider that when you are sizing your touch input. Especially consider that when you are spacing two touch targets near one another. You need to judge it for yourself, but items that are next to each other and are each 100x100 should be fine when it comes to selecting items individually. Smaller targets than that are ok provided that you leave space between them. · You want your users to have a pleasant experience. Making touch controls too small or too close to one another will make them nervous about whether they will touch the right target. Take this into account when you plan out your game initially. If possible, do some quick size mockups on an actual phone using colored rectangles that you position and size where you plan to have your game controls. Adjust as necessary. · People do not have transparent hands! Nor are their hands the size of a mouse pointer icon. Consider leaving a dedicated space for input rather than forcing the user to cover up to one-third of the screen with a finger just to play the game. · Another benefit of designing your controls to use a dedicated area is that you’re less likely to have players moving their finger(s) so frantically that they accidentally hit the back button, start button, or search button (many phones have one or more of these on the screen itself – it’s easy to hit one by accident and really annoying if you hit, e.g., the search button and then quickly tap back only to find out that the game didn’t save your progress such that you just wasted all the time you spent playing). · People do not like doing somersaults in order to move something forward with accelerometer-based controls. Test your accelerometer-based controls extensively and get a lot of feedback. Very well-known games from noted publishers have created really bad accelerometer controls and been virtually unplayable as a result. Also be wary of exceptions and other possible failures that the documentation warns about. · When done properly, the accelerometer can add a nice touch to your game (see, e.g. ilomilo where the accelerometer was used to move the background; it added a nice touch without frustrating the user; I also think CarniVale does direct accelerometer controls very well). However, if done poorly, it will make your game an abomination unto the Marketplace. Days, weeks, perhaps even months of development time that you will never get back. I won’t name names; you can search the marketplace for games with terrible reviews and you’ll find them. Graphics · The maximum frame rate is 30 frames per second. This was set as a compromise between battery life and quality. · At least one model of phone is known to have a screen refresh rate that is between 59 and 60 hertz. Because of this, using a fixed time step with a target frame rate of 30 will cause a slight internal delay to build up as the framework is forced to wait slightly for the next refresh. Eventually the delay will get to the point where a draw is skipped in order to recover from the delay. (See Nick's comment below for clarification.) · To deal with that delay, you can either stay with a fixed time step and set the frame rate slightly lower or else you can go to a variable time step and make sure to adjust all of your update data (e.g. player movement distance) to take into account the elapsed time from the last update. A variable time step makes your update logic slightly more complicated but will avoid frame skips entirely. · Currently there are no custom shaders. This might change in the future (there is no hardware limitation preventing it; it simply wasn’t a feature that could be implemented in the time available before launch). · There are five built-in shaders. You can create a lot of nice effects with the built-in shaders. · There is more power on the CPU than there is on the GPU so things you might typically off-load to the GPU will instead make sense to do on the CPU side. · This is a phone. It is not a PC. It is not an Xbox 360. The emulator runs on a PC and uses the full power of your PC. It is very good for testing your code for bugs and doing early prototyping and layout. You should not use it to measure performance. Use actual phone hardware instead. · There are many phone models, each of which has slightly different performance levels for I/O, screen blitting, CPU performance, etc. Do not take your game right to the performance limit on your phone since for some other phones you might be crossing their limits and leaving players with a bad experience. Leave a cushion to account for hardware differences. · Smaller screened phones will have slightly more dots per inch (dpi). Larger screened phones will have slightly less. Either way, the dpi will be much higher than the typical 96 found on most computer screens. Make sure that whoever is doing art for your game takes this into account. · Screens are only required to have 16 bit color (65,536 colors). This is common among smart phones. Using gradients on a 16 bit display can produce an ugly artifact known as banding. Banding is when, rather than a smooth transition from one color to another, you instead see distinct lines. Be careful to avoid this when possible. Banding can be avoided through careful art creation. Its effects can be minimized and even unnoticeable when the texture in question is always moving. You should be careful not to rely on “looks good on my phone” since some phones do have 32-bit displays and thus you’ll find yourself wondering why you’re getting bad reviews that complain about the graphics. Avoid gradients; if you can’t, make sure they are 16-bit safe. Audio · Never rely on sounds as your sole signal to the player that something is happening in the game. They might have the sound off. They might be playing somewhere loud. Etc. · You have to provide controls to disable sound & music. These should be separate. · On at least one model of phone, the volume control API currently has no effect. Players can adjust sound with their hardware volume buttons, but in game selectors simply won’t work. As such, it may not be worth the effort of providing anything beyond on/off switches for sound and music. · MediaPlayer.GameHasControl will return true when a game is hooked up to a PC running Zune. When Zune is running, any attempts to do anything (beyond check GameHasControl) with MediaPlayer will cause an exception to be thrown. If this exception is thrown, catch it and disable music. Exceptions take time to propagate; you don’t want one popping up in every single run of your game’s Update method. · Remember that players can already be listening to music or using the FM radio. In this case GameHasControl will be false and you should handle this appropriately. You can, alternately, ask the player for permission to stop their current music and play your music instead, but the (current) requirement that you restore their music when done is very hard (if not impossible) to deal with. · You can still play sound effects even when the game doesn’t have control of the music, but don’t think this is a backdoor to playing music. Your game will fail certification if your “sound effect” seems to be more like music in scope and length.

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  • Determining cause of high NFS/IO utilization without iotop

    - by Matt
    I have a server that is doing an NFSv4 export for user's home directories. There are roughly 25 users (mostly developers/analysts) and about 40 servers mounting the home directory export. Performance is miserable, with users often seeing multi-second lags for simple commands (like ls, or writing a small text file). Sometimes the home directory mount completely hangs for minutes, with users getting "permission denied" errors. The hardware is a Dell R510 with dual E5620 CPUs and 8 GB RAM. There are eight 15k 2.5” 600 GB drives (Seagate ST3600057SS) configured in hardware RAID-6 with a single hot spare. RAID controller is a Dell PERC H700 w/512MB cache (Linux sees this as a LSI MegaSAS 9260). OS is CentOS 5.6, home directory partition is ext3, with options “rw,data=journal,usrquota”. I have the HW RAID configured to present two virtual disks to the OS: /dev/sda for the OS (boot, root and swap partitions), and /dev/sdb for the home directories. What I find curious, and suspicious, is that the sda device often has very high utilization, even though it only contains the OS. I would expect this virtual drive to be idle almost all the time. The system is not swapping, according to "free" and "vmstat". Why would there be major load on this device? Here is a 30-second snapshot from iostat: Time: 09:37:28 AM Device: rrqm/s wrqm/s r/s w/s rkB/s wkB/s avgrq-sz avgqu-sz await svctm %util sda 0.00 44.09 0.03 107.76 0.13 607.40 11.27 0.89 8.27 7.27 78.35 sda1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 sda2 0.00 44.09 0.03 107.76 0.13 607.40 11.27 0.89 8.27 7.27 78.35 sdb 0.00 2616.53 0.67 157.88 2.80 11098.83 140.04 8.57 54.08 4.21 66.68 sdb1 0.00 2616.53 0.67 157.88 2.80 11098.83 140.04 8.57 54.08 4.21 66.68 dm-0 0.00 0.00 0.03 151.82 0.13 607.26 8.00 1.25 8.23 5.16 78.35 dm-1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 dm-2 0.00 0.00 0.67 2774.84 2.80 11099.37 8.00 474.30 170.89 0.24 66.84 dm-3 0.00 0.00 0.67 2774.84 2.80 11099.37 8.00 474.30 170.89 0.24 66.84 Looks like iotop is the ideal tool to use to sniff out these kinds of issues. But I'm on CentOS 5.6, which doesn't have a new enough kernel to support that program. I looked at Determining which process is causing heavy disk I/O?, and besides iotop, one of the suggestions said to do a "echo 1 /proc/sys/vm/block_dump". I did that (after directing kernel messages to tempfs). In about 13 minutes I had about 700k reads or writes, roughly half from kjournald and the other half from nfsd: # egrep " kernel: .*(READ|WRITE)" messages | wc -l 768439 # egrep " kernel: kjournald.*(READ|WRITE)" messages | wc -l 403615 # egrep " kernel: nfsd.*(READ|WRITE)" messages | wc -l 314028 For what it's worth, for the last hour, utilization has constantly been over 90% for the home directory drive. My 30-second iostat keeps showing output like this: Time: 09:36:30 PM Device: rrqm/s wrqm/s r/s w/s rkB/s wkB/s avgrq-sz avgqu-sz await svctm %util sda 0.00 6.46 0.20 11.33 0.80 71.71 12.58 0.24 20.53 14.37 16.56 sda1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 sda2 0.00 6.46 0.20 11.33 0.80 71.71 12.58 0.24 20.53 14.37 16.56 sdb 137.29 7.00 549.92 3.80 22817.19 43.19 82.57 3.02 5.45 1.74 96.32 sdb1 137.29 7.00 549.92 3.80 22817.19 43.19 82.57 3.02 5.45 1.74 96.32 dm-0 0.00 0.00 0.20 17.76 0.80 71.04 8.00 0.38 21.21 9.22 16.57 dm-1 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 dm-2 0.00 0.00 687.47 10.80 22817.19 43.19 65.48 4.62 6.61 1.43 99.81 dm-3 0.00 0.00 687.47 10.80 22817.19 43.19 65.48 4.62 6.61 1.43 99.82

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  • PC runs very slowly for no apparent reason

    - by GalacticCowboy
    I have a Dell Latitude D820 that I've owned for about 2.5 years. It is a Core 2 Duo T7200 2.0GHz, with 2 GB of RAM, an 80 GB hard drive and an NVidia Quadro 120M video card. The computer was purchased in late November of 2006 with XP Pro, and included a free upgrade to Vista Business. (Vista was available on MSDN but not yet via retail, so the Vista Business upgrades weren't shipped until March of '07.) Since we had an MSDN subscription at the time, I installed Vista Ultimate on it pretty much as soon as I got it. It ran happily until sometime in the spring of 2007 when Media Center (which I had never used except to watch DVDs) started throwing some kind of bizarre SQL (CE?) error. This error would pop up at random times just while using the computer. Furthermore, Media Center would no longer start. I never identified the cause of this error. I had the Vista Business upgrade by this time, so I nuked the machine, installed XP and all the drivers, and then the Vista Business upgrade. Again, it ran happily for a few months and then started behaving badly once again. Vista Business doesn't have Media Center, so this exhibited completely unrelated symptoms. For no apparent reason and at fairly random times, the machine would suddenly appear to freeze up or run very slowly. For example, launching a new application window (any app) might take 30-45 seconds to paint fully. However, Task Manager showed very low CPU load, memory, etc. I tried all the normal stuff (chkdsk, defrag, etc.) and ran several diagnostic programs to try to identify any problems, but none found anything. It eventually reached the point that the computer was all but unusable, so I nuked it again and installed XP. This time I decided to stick with XP instead of going to Vista. However, within the past couple of months it has started to exhibit the same symptoms in XP that I used to see in Vista. The computer is still under Dell warranty until December, but so far they aren't any help unless I can identify a specific problem. A friend (partner in a now-dead business) has an identical machine that was purchased at the same time. His machine exhibits none of these symptoms, which leads me to believe it is a hardware issue, but I can't figure out how to identify it. Any ideas? Utilities? Seen something similar? At this point I can't even identify any pattern to the behavior, but would be willing to run a "stress test"-style app for as long as a couple days if I had any hope that it would find something. EDIT July 17 I'm testing jerryjvl's answer regarding the video card, though I'm not sure it fully explains the symptoms yet. This morning I ran a video stress test. The test itself ran fine, but immediately afterward the PC started acting up again. I left ProcExp open and various system processes were consuming 50-60% of the CPU but with no apparent reason. For example, "services.exe" was eating about 40%, but the sum of its child processes wasn't higher than about 5%. I left it alone for several minutes to settle down, and then it was fine again. I used the "video card stability test" from firestone-group.com. Its output isn't very detailed, but it at least exercises the hardware pretty hard. EDIT July 22 Thanks for your excellent suggestions. Here is an update on what I have tried so far. Ran memtest86, SeaTools (Seagate), Hitachi drive fitness test, video card stability test (mentioned above). The video card test was the only one that seemed to produce any results, though it didn't occur during the actual test. I defragged the drive (again...) with JkDefrag I dropped the video card

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  • Looking for advice on Hyper-v storage replication

    - by Notre1
    I am designing a 2-host Hyper-V R2 cluster with 6-10 guests stored on a SMB iSCSI SAN device (probably Promise VessRAID). I will be getting at least two of the SAN devices and need to eliminate the storage a single point of failure. Ideally, that would involve real-time failover for the storage, like the Windows failover clustering does for the hosts. This design will be used at around six of our sites, and I would like to allow for us to eventually setup a cluster at colocation site and replicate each site's VMs there for DR. (Ideally a live multi-site cluster, but a manual import of the VMs would be fine for this sort of DR.) The tools that come with enterprise SANs, like EMC and NetApp, seem to be the most commonly used items for a Hyper-V cluster, but I can't afford their prices with my budget. Outside of them, the two tools that seem to be most common for Hyper-V storage replication are SteelEye (now SIOS) DataKeeper Cluster Edition and Double-Take Availability. Originally, I was planning on using Clustered Shared Volume(s) (CSV), but it seems like replication support for these is either not available or brand new in both these products. It looks like CSVs are supported in Double-Take 5.22, see this discussion, but I don't think I want to run something that new in production. Right now, it seems like the best option for me is not to implement CSVs, implement some sort of storage replication, and upgrade to CSVs at a later date once replicating them is more mature. I would love to have live migration, and CSVs are not required for live migration if you are using one LUN per VM, so I guess this is what I'll do. I would prefer to stick to the using the Microsoft Windows Server and Hyper-V tools and features as much as possible. From that standpoint, SteelEye looks more appealing than Double-Take because they make the DataKeeper volume(s) available to the Failover Clustering Manager and then failover clustering is all configured and managed through the native Microsoft tools. Double-Take says that "clustered Hyper-V hosts are not supported," and Double-Take Availability itself seems to be what is used for the actual clustering and failover. Does anyone know if any of these replication tools work with more than two hosts in the cluster? All the information I can find on the web only uses two hosts in their examples. Are there any better tools than SteelEye and Double-Take for doing what I am trying to do, which is eliminate the storage as as single point of failure? Neverfail, AppAssure, and DataCore all seem to offer similar functionality, but they don't seems to be as popular as SteelEye and Double-Take. I have seen a number of people suggest using Starwind iSCSI SAN software for the shared storage, which includes replication (and CSV replication at that). There are a couple of reasons I have not seriously considered this route: 1) The company I work for is exclusively a Dell shop and Dell does not have any servers with that I can pack with more than six 3.5" SATA drives. 2) In the future, it could be advantegous for us to not be locked into a particular brand or type of storage and third-party replication softwares all allow replication to heterogeneous storage devices. I am pretty new to iSCSI and clustering, so please let me know if it looks like I am planning something that goes against best practices or overlooking/missing something.

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  • Setup access to SAS RAID drives with NTFS partitions on CentOS Machine

    - by Quanano
    We have a Dell Poweredge 2900 system with Adaptec 39320A SCSI CONTROLLER CARD and 4 SAS hard drives attached, with NTFS partitions on them. We installed CentOS on the other raid array with a different controller and it is working fine. We are now trying to access the drives shown above and they are not being shown in /dev as sdb, etc. sda is the drive that we installed centos on and it has sda1, sda2, sda3, etc. The CDROM has been picked up as well. If I scan for scsi devices then the perc and adaptec controllers are both found. sg0 is the CDROM and sg2 is the centos installed, however I think sg1 is the other drive but I cannot see anyway to mount the partitions, as only the drive is listed in /dev. Thanks. EXTRA INFO fdisk -l Disk /dev/sda: 72.7 GB, 72746008576 bytes 255 heads, 63 sectors/track, 8844 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x11e3119f Device Boot Start End Blocks Id System /dev/sda1 * 1 64 512000 83 Linux Partition 1 does not end on cylinder boundary. /dev/sda2 64 8845 70528000 8e Linux LVM Disk /dev/mapper/vg_lal2server-lv_root: 34.4 GB, 34431041536 bytes 255 heads, 63 sectors/track, 4186 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x00000000 Disk /dev/mapper/vg_lal2server-lv_root doesn't contain a valid partition table Disk /dev/mapper/vg_lal2server-lv_swap: 21.1 GB, 21139292160 bytes 255 heads, 63 sectors/track, 2570 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x00000000 Disk /dev/mapper/vg_lal2server-lv_swap doesn't contain a valid partition table Disk /dev/mapper/vg_lal2server-lv_home: 16.6 GB, 16647192576 bytes 255 heads, 63 sectors/track, 2023 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x00000000 Disk /dev/mapper/vg_lal2server-lv_home doesn't contain a valid partition table These are all from the install hdd not the additional hard drives modprobe a320raid FATAL: Module a320raid not found. lsscsi -v [0:0:0:0] cd/dvd TSSTcorp CDRWDVD TS-H492C DE02 /dev/sr0 dir: /sys/bus/scsi/devices/0:0:0:0 [/sys/devices/pci0000:00/0000:00:1f.1/host0/target0:0:0/0:0:0:0] [4:0:10:0] enclosu DP BACKPLANE 1.05 - dir: /sys/bus/scsi/devices/4:0:10:0 [/sys/devices/pci0000:00/0000:00:05.0/0000:01:00.0/0000:02:0e.0/host4/target4:0:10/4:0:10:0] [4:2:0:0] disk DELL PERC 5/i 1.03 /dev/sda dir: /sys/bus/scsi/devices/4:2:0:0 [/sys/devices/pci0000:00/0000:00:05.0/0000:01:00.0/0000:02:0e.0/host4/target4:2:0/4:2:0:0] . lsmod Module Size Used by fuse 66285 0 des_generic 16604 0 ecb 2209 0 md4 3461 0 nls_utf8 1455 0 cifs 278370 0 autofs4 26888 4 ipt_REJECT 2383 0 ip6t_REJECT 4628 2 nf_conntrack_ipv6 8748 2 nf_defrag_ipv6 12182 1 nf_conntrack_ipv6 xt_state 1492 2 nf_conntrack 79453 2 nf_conntrack_ipv6,xt_state ip6table_filter 2889 1 ip6_tables 19458 1 ip6table_filter ipv6 322029 31 ip6t_REJECT,nf_conntrack_ipv6,nf_defrag_ipv6 bnx2 79618 0 ses 6859 0 enclosure 8395 1 ses dcdbas 9219 0 serio_raw 4818 0 sg 30124 0 iTCO_wdt 13662 0 iTCO_vendor_support 3088 1 iTCO_wdt i5000_edac 8867 0 edac_core 46773 3 i5000_edac i5k_amb 5105 0 shpchp 33482 0 ext4 364410 3 mbcache 8144 1 ext4 jbd2 88738 1 ext4 sd_mod 39488 3 crc_t10dif 1541 1 sd_mod sr_mod 16228 0 cdrom 39771 1 sr_mod megaraid_sas 77090 2 aic79xx 129492 0 scsi_transport_spi 26151 1 aic79xx pata_acpi 3701 0 ata_generic 3837 0 ata_piix 22846 0 radeon 1023359 1 ttm 70328 1 radeon drm_kms_helper 33236 1 radeon drm 230675 3 radeon,ttm,drm_kms_helper i2c_algo_bit 5762 1 radeon i2c_core 31276 4 radeon,drm_kms_helper,drm,i2c_algo_bit dm_mirror 14101 0 dm_region_hash 12170 1 dm_mirror dm_log 10122 2 dm_mirror,dm_region_hash dm_mod 81500 11 dm_mirror,dm_log

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  • Looking for advice on Hyper-v storage replication

    - by Notre1
    I am designing a 2-host Hyper-V R2 cluster with 6-10 guests stored on a SMB iSCSI SAN device (probably Promise VessRAID). I will be getting at least two of the SAN devices and need to eliminate the storage a single point of failure. Ideally, that would involve real-time failover for the storage, like the Windows failover clustering does for the hosts. This design will be used at around six of our sites, and I would like to allow for us to eventually setup a cluster at colocation site and replicate each site's VMs there for DR. (Ideally a live multi-site cluster, but a manual import of the VMs would be fine for this sort of DR.) The tools that come with enterprise SANs, like EMC and NetApp, seem to be the most commonly used items for a Hyper-V cluster, but I can't afford their prices with my budget. Outside of them, the two tools that seem to be most common for Hyper-V storage replication are SteelEye (now SIOS) DataKeeper Cluster Edition and Double-Take Availability. Originally, I was planning on using Clustered Shared Volume(s) (CSV), but it seems like replication support for these is either not available or brand new in both these products. It looks like CSVs are supported in Double-Take 5.22, see this discussion, but I don't think I want to run something that new in production. Right now, it seems like the best option for me is not to implement CSVs, implement some sort of storage replication, and upgrade to CSVs at a later date once replicating them is more mature. I would love to have live migration, and CSVs are not required for live migration if you are using one LUN per VM, so I guess this is what I'll do. I would prefer to stick to the using the Microsoft Windows Server and Hyper-V tools and features as much as possible. From that standpoint, SteelEye looks more appealing than Double-Take because they make the DataKeeper volume(s) available to the Failover Clustering Manager and then failover clustering is all configured and managed through the native Microsoft tools. Double-Take says that "clustered Hyper-V hosts are not supported," and Double-Take Availability itself seems to be what is used for the actual clustering and failover. Does anyone know if any of these replication tools work with more than two hosts in the cluster? All the information I can find on the web only uses two hosts in their examples. Are there any better tools than SteelEye and Double-Take for doing what I am trying to do, which is eliminate the storage as as single point of failure? Neverfail, AppAssure, and DataCore all seem to offer similar functionality, but they don't seems to be as popular as SteelEye and Double-Take. I have seen a number of people suggest using Starwind iSCSI SAN software for the shared storage, which includes replication (and CSV replication at that). There are a couple of reasons I have not seriously considered this route: 1) The company I work for is exclusively a Dell shop and Dell does not have any servers with that I can pack with more than six 3.5" SATA drives. 2) In the future, it could be advantegous for us to not be locked into a particular brand or type of storage and third-party replication softwares all allow replication to heterogeneous storage devices. I am pretty new to iSCSI and clustering, so please let me know if it looks like I am planning something that goes against best practices or overlooking/missing something.

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  • ipad video format

    - by Mike
    When you use iTunes to sync your videos with the iPhone the videos are always saved with no more than 640 pixels wide, if I am not wrong. What about the iPad? What is the size of videos iTunes syncs with iPad? 1024x768? and what if the video has a dimension below 1024x768? Will it scale up? or will it keep the video at low res and scale when you play? The question is because I am using the MPMoviePlayerController and I need to know what resolutions to expect, so I can adjust the interface. thanks.

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  • How to handle Booleans/CheckBoxes in ASP.NET MVC 2 with DataAnnotations?

    - by asp_net
    I've got a view model like this: public class SignUpViewModel { [Required(ErrorMessage = "Bitte lesen und akzeptieren Sie die AGB.")] [DisplayName("Ich habe die AGB gelesen und akzeptiere diese.")] public bool AgreesWithTerms { get; set; } } The view markup code: <%= Html.CheckBoxFor(m => m.AgreesWithTerms) %> <%= Html.LabelFor(m => m.AgreesWithTerms)%> The result: No validation is executed. That's okay so far because bool is a value type and never null. But even if I make AgreesWithTerms nullable it won't work because the compiler shouts "Templates can be used only with field access, property access, single-dimension array index, or single-parameter custom indexer expressions." So, what's the correct way to handle this?

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  • JScrollPane and JList auto scroll

    - by dododedodonl
    Hi All, I've got the next code: listModel = new DefaultListModel(); listModel.addElement(dateFormat.format(new Date()) + ": Msg1"); messageList = new JList(listModel); messageList.setLayoutOrientation(JList.VERTICAL); messageScrollList = new JScrollPane(messageList); messageScrollList.setPreferredSize(new Dimension(500, 200)); messageScrollList.getVerticalScrollBar().addAdjustmentListener(new AdjustmentListener() { public void adjustmentValueChanged(AdjustmentEvent e) { e.getAdjustable().setValue(e.getAdjustable().getMaximum()); } }); It auto scrolls down. But, if I try to scroll back up to re-read a message, it forces a scroll down. How can I fix this?

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  • Randomly displayed flashing lines, no response to all shortcuts, just power off. [syslog included]

    - by B. Roland
    Hello! I have an old machine, and I want to use for that to learn employees how to use Ubuntu, and to be easyer to switch from Windows. I've been installed 10.04, and updated, but this strange stuff is happend. Graphical installion failed, same strange thing. With alternate workd. Sometimes, when I boot up, a boot message displayed: Keyboard failure..., often diplayed after reboot, and after shutdown, when I haven't plugged off from AC. I replaced the keyboard yet, same failure... If I powered off, and plugged off from AC, no keyboard problems displayed in boot time. Details Configuration: Dell OptiPlex GX60 - in original cover, no changes. 256 MB DDR 166 MHz Intel® Celeron® Processor 2.40 GHz Dell 0C3207 Base Board I know, that is not enough, but I have three other Nec compuers, with nearly similar config, and they works well with 9.10, 10.04, 10.10. Live CDs I've been tried with 10.04 and 10.10, but the problem is displayed too. With 9.10 no strange things displayed, but it froze, during a simple apt-get install. Syslog An error loop is logged here, but I paste the whole startup and error lines. The flashing lines are displayed sometimes immediately after login, but sometimes after 10 minutes, but once occured, that nothing happend. Strange thing is displayed immediately after login: here. An other boot, after some minutes, strange lines, and loop in log appeard: here. The loop should be that: Jan 23 00:20:08 machine_name kernel: [ 46.782212] [drm:i915_gem_entervt_ioctl] *ERROR* Reenabling wedged hardware, good luck Jan 23 00:20:08 machine_name kernel: [ 47.100033] [drm:i915_hangcheck_elapsed] *ERROR* Hangcheck timer elapsed... GPU hung Jan 23 00:20:08 machine_name kernel: [ 47.100045] render error detected, EIR: 0x00000000 Jan 23 00:20:08 machine_name kernel: [ 47.101487] [drm:i915_do_wait_request] *ERROR* i915_do_wait_request returns -5 (awaiting 16 at 9) Jan 23 00:20:11 machine_name kernel: [ 49.152020] [drm:i915_gem_idle] *ERROR* hardware wedged Jan 23 00:20:11 machine_name gdm-simple-slave[1245]: WARNING: Unable to load file '/etc/gdm/custom.conf': No such file or directory Jan 23 00:20:11 machine_name acpid: client 1239[0:0] has disconnected Jan 23 00:20:11 machine_name acpid: client connected from 1247[0:0] Jan 23 00:20:11 machine_name acpid: 1 client rule loaded UPDATE Added syslog things: before errors, error loop, the complete shutdown(after the big updates): Jan 28 20:40:30 machine_name rtkit-daemon[1339]: Sucessfully called chroot. Jan 28 20:40:30 machine_name rtkit-daemon[1339]: Sucessfully dropped privileges. Jan 28 20:40:30 machine_name rtkit-daemon[1339]: Sucessfully limited resources. Jan 28 20:40:30 machine_name rtkit-daemon[1339]: Running. Jan 28 20:40:30 machine_name rtkit-daemon[1339]: Watchdog thread running. Jan 28 20:40:30 machine_name rtkit-daemon[1339]: Canary thread running. Jan 28 20:40:30 machine_name rtkit-daemon[1339]: Sucessfully made thread 1337 of process 1337 (n/a) owned by '1001' high priority at nice level -11. Jan 28 20:40:30 machine_name rtkit-daemon[1339]: Supervising 1 threads of 1 processes of 1 users. Jan 28 20:40:32 machine_name rtkit-daemon[1339]: Sucessfully made thread 1345 of process 1337 (n/a) owned by '1001' RT at priority 5. Jan 28 20:40:32 machine_name rtkit-daemon[1339]: Supervising 2 threads of 1 processes of 1 users. Jan 28 20:40:32 machine_name rtkit-daemon[1339]: Sucessfully made thread 1349 of process 1337 (n/a) owned by '1001' RT at priority 5. Jan 28 20:40:32 machine_name rtkit-daemon[1339]: Supervising 3 threads of 1 processes of 1 users. Jan 28 20:40:37 machine_name pulseaudio[1337]: ratelimit.c: 2 events suppressed Jan 28 20:41:33 machine_name AptDaemon: INFO: Initializing daemon Jan 28 20:41:44 machine_name kernel: [ 167.691563] lo: Disabled Privacy Extensions Jan 28 20:47:33 machine_name AptDaemon: INFO: Quiting due to inactivity Jan 28 20:47:33 machine_name AptDaemon: INFO: Shutdown was requested Jan 28 20:59:50 machine_name kernel: [ 1253.840513] lo: Disabled Privacy Extensions Jan 28 21:17:02 machine_name CRON[1874]: (root) CMD ( cd / && run-parts --report /etc/cron.hourly) Jan 28 21:17:38 machine_name kernel: [ 2321.553239] lo: Disabled Privacy Extensions Jan 28 22:07:44 machine_name kernel: [ 5327.840254] lo: Disabled Privacy Extensions Jan 28 22:17:02 machine_name CRON[2665]: (root) CMD ( cd / && run-parts --report /etc/cron.hourly) Jan 28 22:32:38 machine_name sudo: pam_sm_authenticate: Called Jan 28 22:32:38 machine_name sudo: pam_sm_authenticate: username = [some_user] Jan 28 22:32:38 machine_name sudo: pam_sm_authenticate: /home/some_user is already mounted Jan 28 22:57:03 machine_name kernel: [ 8286.641472] lo: Disabled Privacy Extensions Jan 28 22:57:24 machine_name sudo: pam_sm_authenticate: Called Jan 28 22:57:24 machine_name sudo: pam_sm_authenticate: username = [some_user] Jan 28 22:57:24 machine_name sudo: pam_sm_authenticate: /home/some_user is already mounted Jan 28 23:07:42 machine_name kernel: [ 8925.272030] [drm:i915_hangcheck_elapsed] *ERROR* Hangcheck timer elapsed... GPU hung Jan 28 23:07:42 machine_name kernel: [ 8925.272048] render error detected, EIR: 0x00000000 Jan 28 23:07:42 machine_name kernel: [ 8925.272093] [drm:i915_do_wait_request] *ERROR* i915_do_wait_request returns -5 (awaiting 171453 at 171452) Jan 28 23:07:45 machine_name kernel: [ 8928.868041] [drm:i915_gem_idle] *ERROR* hardware wedged Jan 28 23:08:10 machine_name acpid: client 925[0:0] has disconnected Jan 28 23:08:10 machine_name acpid: client connected from 8127[0:0] Jan 28 23:08:10 machine_name acpid: 1 client rule loaded Jan 28 23:08:11 machine_name kernel: [ 8955.046248] [drm:i915_gem_entervt_ioctl] *ERROR* Reenabling wedged hardware, good luck Jan 28 23:08:12 machine_name kernel: [ 8955.364016] [drm:i915_hangcheck_elapsed] *ERROR* Hangcheck timer elapsed... GPU hung Jan 28 23:08:12 machine_name kernel: [ 8955.364027] render error detected, EIR: 0x00000000 Jan 28 23:08:12 machine_name kernel: [ 8955.364407] [drm:i915_do_wait_request] *ERROR* i915_do_wait_request returns -5 (awaiting 171457 at 171452) Jan 28 23:08:14 machine_name kernel: [ 8957.472025] [drm:i915_gem_idle] *ERROR* hardware wedged Jan 28 23:08:14 machine_name acpid: client 8127[0:0] has disconnected Jan 28 23:08:14 machine_name acpid: client connected from 8141[0:0] Jan 28 23:08:14 machine_name acpid: 1 client rule loaded Jan 28 23:08:15 machine_name kernel: [ 8958.671722] [drm:i915_gem_entervt_ioctl] *ERROR* Reenabling wedged hardware, good luck Jan 28 23:08:15 machine_name kernel: [ 8958.988015] [drm:i915_hangcheck_elapsed] *ERROR* Hangcheck timer elapsed... GPU hung Jan 28 23:08:15 machine_name kernel: [ 8958.988026] render error detected, EIR: 0x00000000 Jan 28 23:08:15 machine_name kernel: [ 8958.989400] [drm:i915_do_wait_request] *ERROR* i915_do_wait_request returns -5 (awaiting 171459 at 171452) Jan 28 23:08:16 machine_name init: tty4 main process (848) killed by TERM signal Jan 28 23:08:16 machine_name init: tty5 main process (856) killed by TERM signal Jan 28 23:08:16 machine_name NetworkManager: nm_signal_handler(): Caught signal 15, shutting down normally. Jan 28 23:08:16 machine_name init: tty2 main process (874) killed by TERM signal Jan 28 23:08:16 machine_name init: tty3 main process (875) killed by TERM signal Jan 28 23:08:16 machine_name init: tty6 main process (877) killed by TERM signal Jan 28 23:08:16 machine_name init: cron main process (890) killed by TERM signal Jan 28 23:08:16 machine_name init: tty1 main process (1146) killed by TERM signal Jan 28 23:08:16 machine_name avahi-daemon[644]: Got SIGTERM, quitting. Jan 28 23:08:16 machine_name avahi-daemon[644]: Leaving mDNS multicast group on interface eth0.IPv4 with address 10.238.11.134. Jan 28 23:08:16 machine_name acpid: exiting Jan 28 23:08:16 machine_name init: avahi-daemon main process (644) terminated with status 255 Jan 28 23:08:17 machine_name kernel: Kernel logging (proc) stopped. Jan 28 23:09:00 machine_name kernel: imklog 4.2.0, log source = /proc/kmsg started. Jan 28 23:09:00 machine_name rsyslogd: [origin software="rsyslogd" swVersion="4.2.0" x-pid="516" x-info="http://www.rsyslog.com"] (re)start Jan 28 23:09:00 machine_name rsyslogd: rsyslogd's groupid changed to 103 Jan 28 23:09:00 machine_name rsyslogd: rsyslogd's userid changed to 101 Jan 28 23:09:00 machine_name rsyslogd-2039: Could no open output file '/dev/xconsole' [try http://www.rsyslog.com/e/2039 ] When I hit the On/Off button, the system shuts down normally. May be it a hardware problem, but I don't know... Can you say something useful to solve my problem?

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  • iPhone SDK: How to centre content in a UIScrollView during setZoomScale?

    - by Russell Quinn
    I'm using a UIScrollView to show photos. If they are zoomed out so they are smaller than the scroll view in one dimension then the content is centred using contentInset and contentOffset. This all works fine for scrolling and manual zooming. However, if I use setZoomScale (with animated YES) then when zooming out the scroll view sets the top left edge to 0,0 during the animation and then snaps it back afterwards. It seems like the zoom animation ignores the contentInset and contentOffset settings. Does anyone have any idea how to overcome this problem? Thanks, Russell.

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  • ipad vide format

    - by Mike
    When you use iTunes to sync your videos with the iPhone the videos are always saved with no more than 640 pixels wide, if I am not wrong. What about the iPad? What is the size of videos iTunes syncs with iPad? 1024x768? and what if the video has a dimension below 1024x768? Will it scale up? or will it keep the video at low res and scale when you play? thanks.

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  • What are the video formats supported by MPMoviePlayerController on the iPad?

    - by Mike
    When you use iTunes to sync your videos with the iPhone the videos are always saved with no more than 640 pixels wide, if I am not wrong. What about the iPad? What is the size of videos iTunes syncs with iPad? 1024x768? and what if the video has a dimension below 1024x768? Will it scale up? or will it keep the video at low res and scale when you play? The question is because I am using the MPMoviePlayerController and I need to know what resolutions to expect, so I can adjust the interface. thanks.

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  • ipad video format [closed]

    - by Mike
    When you use iTunes to sync your videos with the iPhone the videos are always saved with no more than 640 pixels wide, if I am not wrong. What about the iPad? What is the size of videos iTunes syncs with iPad? 1024x768? and what if the video has a dimension below 1024x768? Will it scale up? or will it keep the video at low res and scale when you play? thanks.

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  • Java - sorted stack

    - by msr
    Hello, I need a sorted stack. I mean, the element removed from the stack must be the one with great priority. Stack dimension varies a lot (becomes bigger very fast). I need also to search elements in that stack. Does Java give some good implementation for this? What class or algorithm do you suggest for this? I'm using a PriorityQueue right now which I consider reasonable except for searching, so Im wondering if I can use something better. Thanks in advance!

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  • Multidimensional arrays in VB.NET 2010

    - by matt_t
    Is there any way to create a multidinensional array that contains arrays of different lengths (similar to nesting arrays of different lengths in python). Because if I were to declare a variable Dim accounts(2,2) As Integer all 1D arrays at each dimension have the same length. Is there any way to create an array so that this is not the case? e.g The above code would create an array like this: [[0,0],[0,0]] but would it be possible to create this: [[0,0],[0,0,0]] Apologies for the poor explanation but I cannot think of any better ways to explain.

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  • can't get true height/width of object in chrome

    - by Cinaird
    I have a question, if i set a image height in css and try to get height/width i get different results in different browsers. Is there a way to get the same dimension in all browsers? You can find a live example here and the concept is like this: CSS: img{ height:100px; } Script: $(document).ready(function(){ $("#text").append($("#img_0").attr("height")); $("#text").append($("#img_0").attr("width")); }); Output Firefox: img height: 100 img width: 150 Output Chrome: img height: 100 img width: 0 Output Chrome: img height: 100 img width: 93? i have tried this from StackOverflow: stackoverflow.com/questions/1873419/jquery-get-height-width but still get the same result Any one know a good solution?

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  • Make overflow hidden when shrinking div

    - by johnnietheblack
    I have a div with an image in it, and the image is too large for the div. I have solved the overflow problem with the obvious CSS overflow:hidden trick. But, the problem is that when the div's parent resizes (shrinks), the div holding the image won't shrink because of the image in it. Is there a way to have a resizable div with an image in it (almost like a background image) that overflows? MY DIV STRUCTURE: <div id="parent"> <div id="image_holder"> <!-- this image will inevitably be larger than its parent div --> <img src="too_big_for_div.jpg" /> </div> </div> MY CSS: #parent { width:100%;} #image_holder { width:100%; overflow:hidden;} The #image_holder div will not resize to a smaller dimension now. Any ideas?

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  • Wordpress plugin for enhanced WYSIWYG image resizing?

    - by Gnee
    Really, really trying to find a plugin that gives adds functionality to the image-resize functions in Wordpress's WYSIWYG editor. Something where the use of 'Gallery' is not mandatory – just an upload straight from the post editor. In a post, when an image is linked to from another site, there are less options – unlike when an image is uploaded. • You can resize, but it's 100%, 110%, 120%, 130% ....Instead of thumbnail, large, medium, etc, when you upload. •These dimension rarely match the dimensions needed. I know you can type in the W x H in the advanced tab, but my quest to find a better solution is really for the clients using the site. If anyone knows a solution / plugin / modification for this, I'd love to hear it!!

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  • resize image in asp.net

    - by alina
    I have this code to resize an image but the image doesn't look so good: public Bitmap ProportionallyResizeBitmap(Bitmap src, int maxWidth, int maxHeight) { // original dimensions int w = src.Width; int h = src.Height; // Longest and shortest dimension int longestDimension = (w > h) ? w : h; int shortestDimension = (w < h) ? w : h; // propotionality float factor = ((float)longestDimension) / shortestDimension; // default width is greater than height double newWidth = maxWidth; double newHeight = maxWidth / factor; // if height greater than width recalculate if (w < h) { newWidth = maxHeight / factor; newHeight = maxHeight; } // Create new Bitmap at new dimensions Bitmap result = new Bitmap((int)newWidth, (int)newHeight); using (Graphics g = Graphics.FromImage((System.Drawing.Image)result)) g.DrawImage(src, 0, 0, (int)newWidth, (int)newHeight); return result; }

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  • Question on multi-probe Local Sensitive Hashing

    - by Yijinsei
    Hey guys sorry to be asking this kind noob question, but because I really need some guidance on how to use Multi probe LSH pretty urgently, so I did not do much research myself. I realize there is a lib call LSHKIT available that implemented that algorithm, but I have trouble trying to figure out how to use it. Right now, I have a few thousand feature vector 296 dimension, each representing an image. The vector is used to query an user input image, to retrieve the most similar image. The method I used to derive the distance between vector is euclidean distance. I know this might be a rather noob question, but do you guys have knowledge on how should i implement multi probe LSH? I am really very grateful to any answer or response.

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  • WPF Border Thickness increase direction

    - by morsanu
    Hey. Another WPF question. In my XAML code I have a border: <Border x:Name="myBorder" Background="AliceBlue" Width="200" Height="200" BorderThickness="10" BorderBrush="Black"> </Border> and somewhere in code I increase the BorderThickness double thickness = myBorder.BorderThickness.Bottom + 2; myBorder.BorderThickness = new Thickness(thickness); and the result is that the border's weight increases but not outside the 200x200 width-height, but inner, decreasing the dimension. Is there a way to do the opposite?

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  • How to keep the highlight border of a JComponent, when custom border is set

    - by Frederik Wordenskjold
    I have a JTextField, where I've set some custom properties: nameField.setPreferredSize(new Dimension(275,40)); nameField.setBackground(bgColor); nameField.setForeground(txtColor); nameField.setFont(new Font("HelveticaNeue",Font.PLAIN,22)); nameField.setBorder(BorderFactory.createLineBorder(Color.WHITE, 2)); When the component has focus, there is no highlight shown around the field. On a Mac, it is usually a blue glowing rectangle, indicating that this component has focus. If I comment out the nameField.setBorder(...), the highlight reappears. How do I keep the highlight, but also my custom border!? Basically, I just want the highlight-border to show when the component has focus, and no border when the component is unfocused.

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  • Filter elements in PropertyGrid

    - by serhio
    In System.Windows.Forms there are a PropertyGrid that displays properties of an attached object. Let's say MyTextBox : TextBox. Now, I would like to display on it some MyTextBox properties, say only Size, Location and my custom property Date. More that than, I would like to be able to change the real property names, say "Dimension", "Location" and "Starting Date". I saw two projects on this subject : first and second, but first does not work well(for browsable properties), and the second seems to add an event for each property changes, this is not acceptable.

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  • Cost Comparison Hard Disk Drive to Solid State Drive on Price per Gigabyte - dispelling a myth!

    - by tonyrogerson
    It is often said that Hard Disk Drive storage is significantly cheaper per GiByte than Solid State Devices – this is wholly inaccurate within the database space. People need to look at the cost of the complete solution and not just a single component part in isolation to what is really required to meet the business requirement. Buying a single Hitachi Ultrastar 600GB 3.5” SAS 15Krpm hard disk drive will cost approximately £239.60 (http://scan.co.uk, 22nd March 2012) compared to an OCZ 600GB Z-Drive R4 CM84 PCIe costing £2,316.54 (http://scan.co.uk, 22nd March 2012); I’ve not included FusionIO ioDrive because there is no public pricing available for it – something I never understand and personally when companies do this I immediately think what are they hiding, luckily in FusionIO’s case the product is proven though is expensive compared to OCZ enterprise offerings. On the face of it the single 15Krpm hard disk has a price per GB of £0.39, the SSD £3.86; this is what you will see in the press and this is what sales people will use in comparing the two technologies – do not be fooled by this bullshit people! What is the requirement? The requirement is the database will have a static size of 400GB kept static through archiving so growth and trim will balance the database size, the client requires resilience, there will be several hundred call centre staff querying the database where queries will read a small amount of data but there will be no hot spot in the data so the randomness will come across the entire 400GB of the database, estimates predict that the IOps required will be approximately 4,000IOps at peak times, because it’s a call centre system the IO latency is important and must remain below 5ms per IO. The balance between read and write is 70% read, 30% write. The requirement is now defined and we have three of the most important pieces of the puzzle – space required, estimated IOps and maximum latency per IO. Something to consider with regard SQL Server; write activity requires synchronous IO to the storage media specifically the transaction log; that means the write thread will wait until the IO is completed and hardened off until the thread can continue execution, the requirement has stated that 30% of the system activity will be write so we can expect a high amount of synchronous activity. The hardware solution needs to be defined; two possible solutions: hard disk or solid state based; the real question now is how many hard disks are required to achieve the IO throughput, the latency and resilience, ditto for the solid state. Hard Drive solution On a test on an HP DL380, P410i controller using IOMeter against a single 15Krpm 146GB SAS drive, the throughput given on a transfer size of 8KiB against a 40GiB file on a freshly formatted disk where the partition is the only partition on the disk thus the 40GiB file is on the outer edge of the drive so more sectors can be read before head movement is required: For 100% sequential IO at a queue depth of 16 with 8 worker threads 43,537 IOps at an average latency of 2.93ms (340 MiB/s), for 100% random IO at the same queue depth and worker threads 3,733 IOps at an average latency of 34.06ms (34 MiB/s). The same test was done on the same disk but the test file was 130GiB: For 100% sequential IO at a queue depth of 16 with 8 worker threads 43,537 IOps at an average latency of 2.93ms (340 MiB/s), for 100% random IO at the same queue depth and worker threads 528 IOps at an average latency of 217.49ms (4 MiB/s). From the result it is clear random performance gets worse as the disk fills up – I’m currently writing an article on short stroking which will cover this in detail. Given the work load is random in nature looking at the random performance of the single drive when only 40 GiB of the 146 GB is used gives near the IOps required but the latency is way out. Luckily I have tested 6 x 15Krpm 146GB SAS 15Krpm drives in a RAID 0 using the same test methodology, for the same test above on a 130 GiB for each drive added the performance boost is near linear, for each drive added throughput goes up by 5 MiB/sec, IOps by 700 IOps and latency reducing nearly 50% per drive added (172 ms, 94 ms, 65 ms, 47 ms, 37 ms, 30 ms). This is because the same 130GiB is spread out more as you add drives 130 / 1, 130 / 2, 130 / 3 etc. so implicit short stroking is occurring because there is less file on each drive so less head movement required. The best latency is still 30 ms but we have the IOps required now, but that’s on a 130GiB file and not the 400GiB we need. Some reality check here: a) the drive randomness is more likely to be 50/50 and not a full 100% but the above has highlighted the effect randomness has on the drive and the more a drive fills with data the worse the effect. For argument sake let us assume that for the given workload we need 8 disks to do the job, for resilience reasons we will need 16 because we need to RAID 1+0 them in order to get the throughput and the resilience, RAID 5 would degrade performance. Cost for hard drives: 16 x £239.60 = £3,833.60 For the hard drives we will need disk controllers and a separate external disk array because the likelihood is that the server itself won’t take the drives, a quick spec off DELL for a PowerVault MD1220 which gives the dual pathing with 16 disks 146GB 15Krpm 2.5” disks is priced at £7,438.00, note its probably more once we had two controller cards to sit in the server in, racking etc. Minimum cost taking the DELL quote as an example is therefore: {Cost of Hardware} / {Storage Required} £7,438.60 / 400 = £18.595 per GB £18.59 per GiB is a far cry from the £0.39 we had been told by the salesman and the myth. Yes, the storage array is composed of 16 x 146 disks in RAID 10 (therefore 8 usable) giving an effective usable storage availability of 1168GB but the actual storage requirement is only 400 and the extra disks have had to be purchased to get the  IOps up. Solid State Drive solution A single card significantly exceeds the IOps and latency required, for resilience two will be required. ( £2,316.54 * 2 ) / 400 = £11.58 per GB With the SSD solution only two PCIe sockets are required, no external disk units, no additional controllers, no redundant controllers etc. Conclusion I hope by showing you an example that the myth that hard disk drives are cheaper per GiB than Solid State has now been dispelled - £11.58 per GB for SSD compared to £18.59 for Hard Disk. I’ve not even touched on the running costs, compare the costs of running 18 hard disks, that’s a lot of heat and power compared to two PCIe cards!Just a quick note: I've left a fair amount of information out due to this being a blog! If in doubt, email me :)I'll also deal with the myth that SSD's wear out at a later date as well - that's just way over done still, yes, 5 years ago, but now - no.

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