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  • Is there anyway to build a raid system without all drives?

    - by xenoterracide
    I'm building a raid1 (ok it will probably be a raid10,f2 but the difference with 2 drives... isn't much) system with 2 1TB drives. However, 1 of the drives I've ordered is bad so I'm RMA-ing it. I'm wondering if I could partition and install to the 1 drive and then rebuild the array when I get the second drive (after I test it of course) My initial investigation doesn't show me a way of creating the array without specifying all devices... and the device the second drive will be is one that has data that I will need to migrate (plus it's not big enough). Is it possible that I could create an array without specifying all devices? or specify false ones and reconfigure to the right ones later? Or some other method I'm not thinking of.

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  • Best practice Raid groups for EqualLogic PS6510X

    - by 20th Century Boy
    We are thinking about purchasing 4 x EqualLogic PS6510X SANs (the Sumo boxes). Each has 48 x 600GB 10k SAS drives. They will be stacked to form a logical pool of storage (all in the same location). I understand that when you create a RAID group its done on a "per box" basis. So one box could be Raid 50, another Raid 10 etc. My question is, should I make one box a "performance" box ie Raid 10, and the other boxes "standard" ie Raid50? How do people configure their EQL arrays in the real world?

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  • How to move Mdadm RAID drive (EBS based) to different AWS Instance

    - by Stanley
    We have a media-rich web application that is hosted on AWS. We have several Web Servers and we have an NFS server. On the NFS server (Linux server) we have several EBS volumes that are mounted and we've used mdadm to implement the different mounted volumes as a single RAID volume. The Web Servers simply access the NFS storage through a mount point. Amazon has now let us know that they will be performing power maintenance on this server in a couple of days time. Since all our media is on here it would render our site unusable for the hours while Amazon is working on it. We want to try and prevent this downtime. I was thinking that we can prevent server downtime by perhaps setting up a new server temporarily and attaching the EBS drives (raid volume) to that server and have our web servers point there during maintenance. This is a very high risk operation since this involves several terabytes of our production data. What would be the safe way to move over our logical raid drive (md0) to a new amazon instance? I was hoping that I could start with building the new server, mounting the ebs volumes and assembling the RAID partition using mdadm --assemble --scan before unmounting from the existing instance so that I can first test that everything works and thus having it mounted on two instances at the same time, but I don't believe that is possible with the way that filesystems work. How do I move a Linux software RAID to a new machine? suggests a way to move drives, but isn't really a cloud-based question. Perhaps there are simpler ways to prevent system downtime with our solution being hosted on the cloud? I have considered taking an EBS snapshot, but that tries to replicate all the many terabytes of mounted storage, so this is not a practical solution. Any ideas?

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  • which drive do I mount

    - by Crash893
    I have a system hdd then two raid1 hard drives I see that sda1 is the system drive but when i do a fdisk -l I get the following results so which of the following do i need to mount to get the "raid" drive and not the individual hdd? root@Mxxxx-PDC:/etc/samba# fdisk -l Disk /dev/sda: 251.0 GB, 251000193024 bytes 255 heads, 63 sectors/track, 30515 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Disk identifier: 0x000762dc Device Boot Start End Blocks Id System /dev/sda1 * 1 30328 243609628+ 83 Linux /dev/sda2 30329 30515 1502077+ 5 Extended /dev/sda5 30329 30515 1502046 82 Linux swap / Solaris Disk /dev/sdb: 400.0 GB, 400088457216 bytes 255 heads, 63 sectors/track, 48641 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Disk identifier: 0x00000000 Device Boot Start End Blocks Id System /dev/sdb1 1 48641 390708801 83 Linux Disk /dev/sdc: 250.0 GB, 250059350016 bytes 255 heads, 63 sectors/track, 30401 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Disk identifier: 0x0009f4b2 Device Boot Start End Blocks Id System /dev/sdc1 * 1 255 2048256 fd Linux raid autodetect /dev/sdc2 256 30401 242147745 fd Linux raid autodetect Disk /dev/sdd: 250.0 GB, 250059350016 bytes 255 heads, 63 sectors/track, 30401 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Disk identifier: 0x000b7f4c Device Boot Start End Blocks Id System /dev/sdd1 * 1 255 2048256 fd Linux raid autodetect /dev/sdd2 256 30401 242147745 fd Linux raid autodetect

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  • breaking mdadm raid and moving to NTFS

    - by daveyt
    I'm running Ubuntu 8 something and my data is on a mirrored pair of 1TB disks formatted as ext3, and the RAID is via mdadm. I want to move to Windows 7 (yeah yeah I know but Linux aint doing it for me at the moment) and migrate the disks to NTFS. My plan is: Break the MDADM RAID (by failing one disk logically) Format the 'failed' disk as NTFS Copy data from the RAID array to the NTFS disk (dont care about perms) Install Windows, (new separate non RAid disk) and my data disk is available. I've researched this and it seems the easiest way. I dont have another disk to back up to so I think this is my only way. Can anyone see a better/easier way?

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  • HP E200i Controlller RAID Configuration fon Win2008 Ent, Sql Server, IIS Apps etc need opinion

    - by mn
    Hello, Actually I run RAID 5 (4 x SAS drives) with Win 2008 Ent(1x host) Win 2008 End(3x guest) Sql Server 2005 Std (on guest) 3 x asp.net applications (on guest) I bought 3 x drives to create additional array (on same controller E200i, I am waiting now for confirmation is it possible to have 3 raids in same controller) I am planning to have 2 x RAID5 (if it is possible) first RAID 5 with all vhd files, systems etc second RAID 5 all data files and transaction logs I am looking for opinion how to optimize data layer (seven drives, one controller).

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  • Linux Software Raid runs checkarray on the First Sunday of the Month? Why?

    - by mgjk
    It looks like Debian has a default to run checkarray on the first Sunday of the month. This causes massive performance problems and heavy disk usage for 12 hours on my 2TB mirror. Doing this "just in case" is bizzare to me. Discovering data out of sync between the two disks without quorum would be a failure anyway. This massive checking could only tell me that I have an unrecoverable drive failure and corrupt data. Which is nice, but not all that helpful. Is it necessary? Given I have no disk errors and no reason to believe my disks have failed, why is this check necessary? Should I take it out of my cron? /etc/cron.d# tail -1 /etc/cron.d/mdadm 57 0 * * 0 root [ -x /usr/share/mdadm/checkarray ] && [ $(date +\%d) -le 7 ] && /usr/share/mdadm/checkarray --cron --all --quiet Thanks for any insight,

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  • How do you expand a raid disk array in a dell 2850?

    - by johnny
    Hi, I have a Dell 2850 and I want to install Windows 2008 Server. Problem is that my C drive only has 16GB of space. The requirements say I need at least 20. I have an open bay for a drive. If I put in another drive, how can I add that to the array and them make it only for the C drive? what do I do? Thank you. edit: I don't want to remove any drives. I just want to add a new one to the existing array. Can I do that and make sure that new drive is for the logical C drive?

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  • Linux Raid: Can mdadm --grow a raid1 while mounted?

    - by Chris
    I have 2 500gb drives in a RAID1 setup that I needed to upgrade for more space. I mdadm --fail'ed each drive in turn and I used dd to copy each drive to it's respective larger drive (2tb each), removed the smaller drives and replaced them with the larger drives, and reassembled the array and forced a resync. So now I've got a 500gb RAID1 sitting on 2TB drives, and wish to grow them. The plan is to use mdadm --manage /dev/md0 --grow to grow them, then boot a rescue cd, assemble the array under that environment, and do the resize2fs on them. Can I use mdadm --grow on a mounted and live filesystem? Also, do I need more options to make sure the grow operation stays raid1?

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  • Windows 7 Sharing issue on RAID 5 Array(s)

    - by K.A.I.N
    Greetings all, I'm having a very odd error with a windows 7 ultimate x64 system. The network system setup is as follows: 2x XP Pro 32 Bit machines 1x Vista ultimate x64 machine 2x Windows 7 x64 Ultimate machines all chained into 1x 16 port netgear prosafe gigabit switch, the windows 7 & vista machines are duplexed. Also there is a router (netgear Rangemax) chained off the switch I am basically using one of the windows 7 machines to host storage & stream media to other machines. To this end i have put 2x 3tb hardware RAID 5 arrays in it and assorted other spare disks which i have shared the roots of. The unusual problems start when i am getting Access denied, Please contact administrator for permission blah blah blah when trying to access both of the RAID 5 arrays but not the other stand alones. I have checked the permission settings, i have added everyone to the read permission for the root, i have tried moving things into sub directories then sharing them. I have tried various setting combinations in HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa and always the same. I have tried flushing caches all round, disabling and re-enabling shares & sharing after restart as well as several other things & the result is always the same... No problem on individual drives but access denied on both the RAID arrays from both XP & Vista & Windows 7 machines. One interesting quirk that may lead to an answer is that there is no "offline status" information regarding the folders when you select the RAID 5s from a windows 7 machine yet there is on the normal drives which say they are online. It is as if the raid is present but turned off or spun down but as far as i was aware windows will spin an array back up on network request and on the machine itself the drives seem to be online and can be accessed. Have to admit this has me stumped. Any suggestions anyone? Thanks in advance for any fellow geek assistance. K.A.I.N

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  • Windows Server 2008 RAID10

    - by JT
    Hello All, I am building a storage system for myself. I have a 16 bay SATA chasis and right now I have 1 x 500GB SATA for booting 8 x 1.5TB for data. 3Ware 9500S-8 RAID card where these 8 drives above are connected to. I am used to linux, but not in the RAID department. I have Windows experience too. What I am looking for is something that I can just let sit, be reliable and use for other items as well. (Like running test websites, Apache, MySQL, etc). This box is private on a Class-C subnet. My thought is to at least consider Windows Server 2008. I especially like the potential for NON-GUI Mode. Can Windows Server 2008 do a Software RAID 10 out of the box? Software RAID is better performance and better in case the raid needs to be moved to another machine? I just want to SCP files, so OpenSSH running on it? Can one install the GUI, but not use it unless they get in a bind? Is Windows a good idea or should I stick to a Linux Software RAID or FreeBSD + ZFS?

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  • Adding third disk as a single disk in a server with an existing RAID1

    - by slowhandsolo
    I've got a ProLiant DL360 G5 server (Fedora 13) with two SAS disks in a hardware RAID 1, working fine. Now I hot plugged another SAS disk. I'd like to configure this new hard disk out of my RAID, as a single non-RAID disk (ex. /dev/sdb). Even after rebooting the server, I can't see the new disk with "fdisk -l". It displays only my hardware RAID, but not the new disk. [root@myserver]# fdisk -l Disco /dev/cciss/c0d0: 300.0 GB, 299966445568 bytes Disposit. Inicio Comienzo Fin Bloques Id Sistema /dev/cciss/c0d0p1 * 1 126 512000 83 Linux /dev/cciss/c0d0p2 126 71798 292422656 8e Linux LVM Disco /dev/dm-0: 234.9 GB, 234881024000 bytes Disco /dev/dm-1: 10.5 GB, 10536091648 bytes Disco /dev/dm-2: 21.0 GB, 20971520000 bytes Disco /dev/dm-3: 31.5 GB, 31474057216 bytes Disco /dev/dm-4: 1577 MB, 1577058304 bytes However, I can see the new disk using the HP Array Configuration Utility CLI for Linux "hpacucli": [root@myserver]# hpacucli => controller slot=0 physicaldrive all show status physicaldrive 1I:1:1 (port 1I:box 1:bay 1, 300 GB): OK physicaldrive 1I:1:2 (port 1I:box 1:bay 2, 300 GB): OK physicaldrive 1I:1:3 (port 1I:box 1:bay 3, 300 GB): OK => controller slot=0 pd all show detail Smart Array P400i in Slot 0 (Embedded) array A physicaldrive 1I:1:1 Port: 1I Box: 1 Bay: 1 physicaldrive 1I:1:2 Port: 1I Box: 1 Bay: 2 **unassigned** physicaldrive 1I:1:3 Port: 1I Box: 1 Bay: 3 Status: OK Drive Type: **Unassigned Drive** As you can see, I've got two SAS disks in a RAID 1 and the new disk as "unassigned". Is there any way to work with the new disk as another non-RAID single disk? If relevant, I want to create a new partition in my new disk, format it with mkfs and mount it, but as I can't see it with fdisk, I don't know how to do it. Thanks!

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  • How to create partition when growing raid5 with mdadm.

    - by hometoast
    I have 4 drives, 2x640GB, and 2x1TB drives. My array is made up of the four 640GB partitions and the beginning of each drive. I want to replace both 640GB with 1TB drives. I understand I need to 1) fail a disk 2) replace with new 3) partition 4) add disk to array My question is, when I create the new partition on the new 1TB drive, do I create a 1TB "Raid Auto Detect" partition? Or do I create another 640GB partition and grow it later? Or perhaps the same question could be worded: after I replace the drives how to I grow the 640GB raid partitions to fill the rest of the 1TB drive? fdisk info: Disk /dev/sdb: 1000.2 GB, 1000204886016 bytes 255 heads, 63 sectors/track, 121601 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Disk identifier: 0xe3d0900f Device Boot Start End Blocks Id System /dev/sdb1 1 77825 625129281 fd Linux raid autodetect /dev/sdb2 77826 121601 351630720 83 Linux Disk /dev/sdc: 1000.2 GB, 1000204886016 bytes 255 heads, 63 sectors/track, 121601 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Disk identifier: 0xc0b23adf Device Boot Start End Blocks Id System /dev/sdc1 1 77825 625129281 fd Linux raid autodetect /dev/sdc2 77826 121601 351630720 83 Linux Disk /dev/sdd: 640.1 GB, 640135028736 bytes 255 heads, 63 sectors/track, 77825 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Disk identifier: 0x582c8b94 Device Boot Start End Blocks Id System /dev/sdd1 1 77825 625129281 fd Linux raid autodetect Disk /dev/sde: 640.1 GB, 640135028736 bytes 255 heads, 63 sectors/track, 77825 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Disk identifier: 0xbc33313a Device Boot Start End Blocks Id System /dev/sde1 1 77825 625129281 fd Linux raid autodetect Disk /dev/md0: 1920.4 GB, 1920396951552 bytes 2 heads, 4 sectors/track, 468846912 cylinders Units = cylinders of 8 * 512 = 4096 bytes Disk identifier: 0x00000000

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  • ubuntu server 12.04 new installation does not boot

    - by itsols
    I've just installed server 12.04 on a new machine. It's got two network cards and two hard drives. During installation it asked me if I wanted to make it RAID and I said ok to that. Finally, it came to the packages options and I chose things like Samba, LAMP, etc. And then it asked to reboot without the CD. Did that and that's where the problem started. Nothing comes on the screen. Only a blinking cursor. Has anyone experienced this problem? I'm guessing that it may be a RAID issue. Not sure. Any thoughts please...

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  • Ubuntu 12.10 "fakeRAID" RAID0 installation

    - by João André
    I have 2 80 Gb HDD's with a RAID 0 motherboard configuration (Intel Z77, fakeRAID) with a 100 Gb partition running Windows 7 and a 60 Gb partition where I would like to install Ubuntu 12.10. However, even though the installer seems to correctly detect the RAID 0 array, GRUB2 is not installed and the computer boots into Windows normally. The same thing does not happen when installing Fedora 17. The installer (Anaconda) also detects the disk array, but GRUB2 installation is successful. What exactly are the differences between Ubiquity and Anaconda? And is there a way to correctly install GRUB2 in a fakeRAID system, since there are no alternative Ubuntu CDs?

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  • How to Setup Software RAID for a Simple File Server on Ubuntu

    - by Sysadmin Geek
    Do you need a file server on the cheap that is easy to setup, “rock solid” reliable with Email Alerting? will show you how to use Ubuntu, software RAID and SaMBa to accomplish just that Latest Features How-To Geek ETC How To Boot 10 Different Live CDs From 1 USB Flash Drive The 20 Best How-To Geek Linux Articles of 2010 The 50 Best How-To Geek Windows Articles of 2010 The 20 Best How-To Geek Explainer Topics for 2010 How to Disable Caps Lock Key in Windows 7 or Vista How to Use the Avira Rescue CD to Clean Your Infected PC Install LibreOffice via PPA and Receive Auto-Updates in Ubuntu Creative Portraits Peek Inside the Guts of Modern Electronics Scenic Winter Lane Wallpaper to Create a Relaxing Mood Access Your Web Apps Directly Using the Context Menu in Chrome The Deep – Awesome Use of Metal Objects as Deep Sea Creatures [Video] Convert or View Documents Online Easily with Zoho, No Account Required

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  • Removing mdadm array and converting to regular disks while preserving data

    - by Jeffrey Kevin Pry
    I have a 6 disk (2TB each) mdadm RAID 5 volume created in Ubuntu 12.04 Server. However, I'm moving to a different solution and want to "unraid" my disks but keep the data. Only 50% is in use. From what I can surmise I basically have to do this recursively for each physical disk. Fail the disk Format the failed disk Move a portion of files to the new disk. Reshape the array Shrink the logical volume md0 This seems like a very time consuming process. Is there an easier way to do this (automatically perhaps) without buying new disks to temporarily hold the data? I am also aware that during this processing my RAID volume will be degraded and vulnerable the entire time. I am not too concerned about this and will be using battery backup and moving the most important files off first. Thank you for your help!

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  • SQLAuthority News – Pinal Dave: Blogger, MVP and now Interviewee by Michael J Swart

    - by pinaldave
    Michael J. Swart is a very unique person. I have often exchanged emails with him and also used a couple of his scripts in my presentations (with his permission). Every time I conduct spatial database presentation, I always start with his script where he has drawn the wonderful image of Botticelli’s Birth of Venus. I often think he is more of a creative artist than IT professional. However, if you read his blog posts and articles, they are top notch and each article is as creative as his caricatures. He is wonderful, inspiring, creative and most importantly, very humble. He recently took my interview and asked me some very interesting question. To answer his question, I had to share some of the interesting aspects of my life which I have had never shared in any interview before. He made me share the following interesting facts. Pinal Dave Caricatures Read my Interview Here are a few questions that I have answered at his blog: How I met my wife? Best moments of my life? How to pronounce my last name? Who inspired me? English as a Third Language. I am also thankful to Michael for drawing my caricature. I really liked it and I am very glad that he took time to do so. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: About Me, Pinal Dave, PostADay, Readers Question, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • SQL SERVER – Interview Questions & Answers Needs Your Help

    - by pinaldave
    About an year ago, I had posted SQL Server related Interview Questions and Answers. It was very well received in community. I have received many comments, suggestions and emails on this subject. I am planning to upgrade the Interview Questions and Answers and take it to next level. Here, I need your help. Please your comments, suggestions, expectation or potential interview Question (along with answer) here. Your input will be very valuable. As time goes by we all learn and get better. There were few things missing at that time when those interview questions and answers were prepared, now is the time to complete the gap and make this interview questions more useful. If you know all, this Question and Answers are not for you. This are for those who is eager to learn and need help in the area. If you do not want to leave a comment, I suggest to send me email at pinal “at” SQLAuthority.com Following is the reproduction of original consolidation post for quick reference. SQL SERVER – 2008 – Interview Questions and Answers – Part 1 SQL SERVER – 2008 – Interview Questions and Answers – Part 2 SQL SERVER – 2008 – Interview Questions and Answers – Part 3 SQL SERVER – 2008 – Interview Questions and Answers – Part 4 SQL SERVER – 2008 – Interview Questions and Answers – Part 5 SQL SERVER – 2008 – Interview Questions and Answers – Part 6 SQL SERVER – 2008 – Interview Questions and Answers – Part 7 SQL SERVER – 2008 – Interview Questions and Answers – Part 8 Download SQL Server 2008 Interview Questions and Answers Complete List Reference : Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, Readers Contribution, Readers Question, SQL, SQL Authority, SQL Documentation, SQL Download, SQL Interview Questions and Answers, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • Linux software RAID6: 3 drives offline - how to force online?

    - by Ole Tange
    This is similar to 3 drives fell out of Raid6 mdadm - rebuilding? except that it is not due to a failing cable. Instead the 3rd drive fell offline during rebuild of another drive. The drive failed with: kernel: end_request: I/O error, dev sdc, sector 293732432 kernel: md/raid:md0: read error not correctable (sector 293734224 on sdc). After rebooting both these sectors and the sectors around them are fine. This leads me to believe the error is intermittent and thus the device simply took too long to error correct the sector and remap it. I expect that no data was written to the RAID after it failed. Therefore I hope that if I can kick the last failing device online that the RAID is fine and that the xfs_filesystem is OK, maybe with a few missing recent files. Taking a backup of the disks in the RAID takes 24 hours, so I would prefer that the solution works the first time. I have therefore set up a test scenario: export PRE=3 parallel dd if=/dev/zero of=/tmp/raid${PRE}{} bs=1k count=1000k ::: 1 2 3 4 5 parallel mknod /dev/loop${PRE}{} b 7 ${PRE}{} \; losetup /dev/loop${PRE}{} /tmp/raid${PRE}{} ::: 1 2 3 4 5 mdadm --create /dev/md$PRE -c 4096 --level=6 --raid-devices=5 /dev/loop${PRE}[12345] cat /proc/mdstat mkfs.xfs -f /dev/md$PRE mkdir -p /mnt/disk2 umount -l /mnt/disk2 mount /dev/md$PRE /mnt/disk2 seq 1000 | parallel -j1 mkdir -p /mnt/disk2/{}\;cp /bin/* /mnt/disk2/{}\;sleep 0.5 & mdadm --fail /dev/md$PRE /dev/loop${PRE}3 /dev/loop${PRE}4 cat /proc/mdstat # Assume reboot so no process is using the dir kill %1; sync & kill %1; sync & # Force fail one too many mdadm --fail /dev/md$PRE /dev/loop${PRE}1 parallel --tag -k mdadm -E ::: /dev/loop${PRE}? | grep Upda # loop 2,5 are newest. loop1 almost newest => force add loop1 Next step is to add loop1 back - and this is where I am stuck. After that do a xfs-consistency check. When that works, check that the solution also works on real devices (such a 4 USB sticks).

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  • Organization &amp; Architecture UNISA Studies &ndash; Chap 6

    - by MarkPearl
    Learning Outcomes Discuss the physical characteristics of magnetic disks Describe how data is organized and accessed on a magnetic disk Discuss the parameters that play a role in the performance of magnetic disks Describe different optical memory devices Magnetic Disk The way data is stored on and retried from magnetic disks Data is recorded on and later retrieved form the disk via a conducting coil named the head (in many systems there are two heads) The writ mechanism exploits the fact that electricity flowing through a coil produces a magnetic field. Electric pulses are sent to the write head, and the resulting magnetic patterns are recorded on the surface below with different patterns for positive and negative currents The physical characteristics of a magnetic disk   Summarize from book   The factors that play a role in the performance of a disk Seek time – the time it takes to position the head at the track Rotational delay / latency – the time it takes for the beginning of the sector to reach the head Access time – the sum of the seek time and rotational delay Transfer time – the time it takes to transfer data RAID The rate of improvement in secondary storage performance has been considerably less than the rate for processors and main memory. Thus secondary storage has become a bit of a bottleneck. RAID works on the concept that if one disk can be pushed so far, additional gains in performance are to be had by using multiple parallel components. Points to note about RAID… RAID is a set of physical disk drives viewed by the operating system as a single logical drive Data is distributed across the physical drives of an array in a scheme known as striping Redundant disk capacity is used to store parity information, which guarantees data recoverability in case of a disk failure (not supported by RAID 0 or RAID 1) Interesting to note that the increase in the number of drives, increases the probability of failure. To compensate for this decreased reliability RAID makes use of stored parity information that enables the recovery of data lost due to a disk failure.   The RAID scheme consists of 7 levels…   Category Level Description Disks Required Data Availability Large I/O Data Transfer Capacity Small I/O Request Rate Striping 0 Non Redundant N Lower than single disk Very high Very high for both read and write Mirroring 1 Mirrored 2N Higher than RAID 2 – 5 but lower than RAID 6 Higher than single disk Up to twice that of a signle disk for read Parallel Access 2 Redundant via Hamming Code N + m Much higher than single disk Highest of all listed alternatives Approximately twice that of a single disk Parallel Access 3 Bit interleaved parity N + 1 Much higher than single disk Highest of all listed alternatives Approximately twice that of a single disk Independent Access 4 Block interleaved parity N + 1 Much higher than single disk Similar to RAID 0 for read, significantly lower than single disk for write Similar to RAID 0 for read, significantly lower than single disk for write Independent Access 5 Block interleaved parity N + 1 Much higher than single disk Similar to RAID 0 for read, lower than single disk for write Similar to RAID 0 for read, generally  lower than single disk for write Independent Access 6 Block interleaved parity N + 2 Highest of all listed alternatives Similar to RAID 0 for read; lower than RAID 5 for write Similar to RAID 0 for read, significantly lower than RAID 5  for write   Read page 215 – 221 for detailed explanation on RAID levels Optical Memory There are a variety of optical-disk systems available. Read through the table on page 222 – 223 Some of the devices include… CD CD-ROM CD-R CD-RW DVD DVD-R DVD-RW Blue-Ray DVD Magnetic Tape Most modern systems use serial recording – data is lade out as a sequence of bits along each track. The typical recording used in serial is referred to as serpentine recording. In this technique when data is being recorded, the first set of bits is recorded along the whole length of the tape. When the end of the tape is reached the heads are repostioned to record a new track, and the tape is again recorded on its whole length, this time in the opposite direction. That process continued back and forth until the tape is full. To increase speed, the read-write head is capable of reading and writing a number of adjacent tracks simultaneously. Data is still recorded serially along individual tracks, but blocks in sequence are stored on adjacent tracks as suggested. A tape drive is a sequential access device. Magnetic tape was the first kind of secondary memory. It is still widely used as the lowest-cost, slowest speed member of the memory hierarchy.

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