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  • How would one build a relational database on a key-value store, a-la Berkeley DB's SQL interface?

    - by coleifer
    I've been checking out Berkeley DB and was impressed to find that it supported a SQL interface that is "nearly identical" to SQLite. http://docs.oracle.com/cd/E17076_02/html/bdb-sql/dbsqlbasics.html#identicalusage I'm very curious, at a high-level, how this kind of interface might have been architected. For instance: since values are "transparent", how do you efficiently query and sort by value how are limits and offsets performed efficiently on large result sets how would the keys be structured and serialized for good average-case performance

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  • Manipulating XML Data in SQL Server

    When the average database developer is obliged to manipulate XML, either shredding it into relational format, or creating it from SQL, it is often done 'at arms length'. A shame, since effective use of techniques that go beyond the basics can save much code, "It really helped us isolate where we were experiencing a bottleneck"- John Q Martin, SQL Server DBA. Get started with SQL Monitor today to solve tricky performance problems - download a free trial

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  • Botnet Malware Sleeps Eight Months Activation, Child Concerns

    Daily Safety Check experts used a computer forensic analysis of a significant botnet that consisted of Carberp and SpyEye malware to come up with the details for their report. The analysis found that the botnet profiled the behavior of the slave computers it infected, similar to surveillance techniques used by law enforcement agencies, for an average of eight months. During the eight months, the botnet analyzed each computer's users and assigned ratings to certain activities to form a complete profile for each. Doing so allowed those behind the scheme to determine which were the most favora...

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  • Microsoft`s SkyDrive Abandons Silverlight

    SkyDrive Microsoft s cloud storage service has just received a hefty makeover that has its users as well as Silverlight developers talking. SkyDrive s site is new and improved and is successful in providing a better user experience but the changes may have some Silverlight developers feeling a bit worried when it comes to Microsoft s future plans for their beloved framework.... Display the VeriSign seal And increase sales by an average of 24%. Start your trial today

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  • Is there a more efficient way to filter large arrays than preg_match()?

    - by hozza
    I have a log that our web application builds. Each month it contains around 16,000 entries of a string with about the average sentence worth of text. To filter/search through these in our admin panel the script uses preg_match() but this seems to be taking ages and timing out on the 30sec limit. I have isolated that it is indeed the preg_match() that causes the time out. Is there a more efficient way to search through values in a large array for a users input?

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  • How to make the most of GWT's "Search queries"?

    - by DisgruntledGoat
    I've been looking at the "Search queries" section in Google Webmaster Tools recently, and it seems like there is a lot of potential there in finding which pages on a site need improvement. I'm trying to figure out exactly what to sort or filter on. Do I look at pages with a low average position? Low impressions but high clicks? Pages that are rising up/falling down the rankings? What is the low-hanging fruit here?

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  • Enterprise SEO, A Wasted Opportunity

    Corporates have embraced the net for quite a while now, but search engine marketing is still considered the lowest form of advertisement. Fair enough, its cheaper than your average TV campaign, but much more targeted and measurable. Spending money on ads isn't everything though, SEO (search engine optimisation) should play a dominant role in the search marketing budget as nothing will drive more visitors to your page than a good ranking on Google. However large enterprises seem to skimp when it comes to SEO and misses out on key opportunities at the same time.

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  • What Does it Cost to Build a Website?

    The Internet is growing by leaps and bounds everyday. Because of this, the average cost to build a website is within most peoples grasp. First of all, you need to understand, there are only 2 tools associated with making and maintaining your own website.

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  • KahelOS (050110) Review

    <b>Desktop Linux Reviews: </b>"KahelOS is essentially a remastered version of Arch Linux. Arch Linux has always had a reputation as being somewhat inaccessible to average desktop users, and KahelOS is an attempt to make Arch Linux more accessible to more people."

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  • What Does it Cost to Build a Website?

    The Internet is growing by leaps and bounds everyday. Because of this, the average cost to build a website is within most peoples grasp. First of all, you need to understand, there are only 2 tools associated with making and maintaining your own website.

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  • Storage Technology for the Home User

    <b>Linux Magazine:</b> "Sometimes you just have to get excited about what you can buy, hold in your hand, and use in your home machines. Let's look at some cool storage technology that the average desktop user can tackle."

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  • Why You Need to Upgrade Your Website Now

    Why Upgrade? Today, having a website for your business is a must. If you are the kind of business that cannot accept anything below average, then you have to take a good look at your existing website right now and see if it is producing great results for you and the business you run.

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  • SEO Pricing

    SEO is very important to the online business with on average the number of leads the search engines produce being anything from 60% - 100% of the visitors to a website. So as an SEO, how do you work out your SEO pricing?

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  • Avoid a Frustrating Website!

    How many times have you come across a website that either does not work or it has issues? We find them all the time and there is almost an endless list of things we find either annoying or not working! For the average person this can be frustrating as often the reason we went to a particular web site was because we were looking for something in particular that that web site supposedly offers.

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  • Avoid a Frustrating Website!

    How many times have you come across a website that either does not work or it has issues? We find them all the time and there is almost an endless list of things we find either annoying or not working! For the average person this can be frustrating as often the reason we went to a particular web site was because we were looking for something in particular that that web site supposedly offers.

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  • Bad disk performance on HP DL360 with Smarty Array P400i RAID controller

    - by sarge
    I have a HP DL360 server with 4x 146GB SAS disks and a Smart Array P400i RAID controller with 256MB cache. The disks are in RAID 5 (3 disks + 1 hot spare). The server is running VMware ESX 3i. The disk write performance is really bad. Here are some numbers: ns1:~# hdparm -tT /dev/sda /dev/sda: Timing cached reads: 3364 MB in 2.00 seconds = 1685.69 MB/sec Timing buffered disk reads: 18 MB in 3.79 seconds = 4.75 MB/sec ns1:~# time sh -c "dd if=/dev/zero of=ddfile bs=8k count=125000 && sync" 125000+0 records in 125000+0 records out 1024000000 bytes (1.0 GB) copied, 282.307 s, 3.6 MB/s real 4m52.003s user 0m2.160s sys 3m10.796s Compared to another server those number are terrible: Dell R200, 2x 500GB SATA disks, PERC raid controller (disks are mirrored). web4:~# hdparm -tT /dev/sda /dev/sda: Timing cached reads: 6584 MB in 2.00 seconds = 3297.79 MB/sec Timing buffered disk reads: 316 MB in 3.02 seconds = 104.79 MB/sec web4:~# time sh -c "dd if=/dev/zero of=ddfile bs=8k count=125000 && sync" 125000+0 records in 125000+0 records out 1024000000 bytes (1.0 GB) copied, 35.2919 s, 29.0 MB/s real 0m36.570s user 0m0.476s sys 0m32.298s The server isn't very loaded and the VMware Infrastructure Client performance monitor is showing 550KBps average read and 1208KBps average write for the last 30 minutes (highest write rate: 6.6MBps). This has been a problem from the start. Any ideas?

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  • PHP-FPM and APC for shared hosting?

    - by Tiffany Walker
    We are looking into finding a way to get APC to only create one cache per account / site. This can be done with Fastcgi (last update 2006…) but with Fastcgid APC will have to create multiple caches for multiple processes run by the same account. To get around this problem, we have been looking into PHP-FPM PHP process manager allows multiple PHP processes to share a single APC cache. But from what I have read (I hope I'm wrong) , even if you create a pool per process, all sites accross all pools will share the same APC cache. This brings us back to the same problem as with shared Memcached: it's not secure ! On php-fpm's site I read that you can chroot php-fpm pools and define a specific UID and GID per pool… if this is the case then shouldn't APC have to use this user and not have access to other pools cache ? An article here (in 2011) suggests that you would need to run one process per pool creating multiple launchers on different ports and different config files with one pool per config file : http://groups.drupal.org/node/198168 Is this still neceessary ? If so what would be the impact of running say 800 processes of php-fpm ? Would it be mainly memory ? If so how can I work out what the memory impact would be ? I guess that it would be better to run 800 times php-fpm then to have accounts creating multiple APC caches for a single site ? If on average an account creates a 50MB cache and creates 3 caches per account that makes 150Mb per account which makes 120GB… However if each account uses on average only 50Mb that would make 40GB We will have at least 128GB of ram on our next server so 40GB is acceptable if running 800 x PHP-FPM does not create an overhead of more than 20GB ! What do you think is PHP-FPM the best way to go to provide secure APC cache on shared hosting with a server that has a decent amount of memory ? Or should I be looking at another system ? Thanks !

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  • Why does traceroute take much longer than ping?

    - by PHP
    How to explain this? C:\Documents and Settings\Administrator>tracert google.com Tracing route to google.com [64.233.189.104] over a maximum of 30 hops: 1 <1 ms <1 ms <1 ms 192.168.0.1 2 7 ms <1 ms <1 ms reserve.cableplus.com.cn [218.242.223.209] 3 108 ms 135 ms 163 ms 211.154.70.10 4 * * * Request timed out. 5 2 ms * 1 ms 211.154.64.114 6 1 ms 1 ms 1 ms 211.154.72.185 7 1 ms 1 ms 1 ms 202.96.222.77 8 2 ms 1 ms 2 ms 61.152.81.145 9 1 ms 2 ms 1 ms 61.152.86.54 10 1 ms 1 ms 1 ms 202.97.33.238 11 2 ms 2 ms 2 ms 202.97.33.54 12 2 ms 1 ms 2 ms 202.97.33.5 13 33 ms 33 ms 33 ms 202.97.61.50 14 34 ms 34 ms 34 ms 202.97.62.214 15 34 ms 186 ms 37 ms 209.85.241.56 16 35 ms 35 ms 44 ms 66.249.94.34 17 34 ms 34 ms 34 ms hkg01s01-in-f104.1e100.net [64.233.189.104] Trace complete. So average time should be :1+7+108+2+1+1+2+1+1+2+2+33+34+34+35+34+34+35+34,which is a lot bigger than ping C:\Documents and Settings\Administrator>ping google.com Pinging google.com [64.233.189.104] with 32 bytes of data: Reply from 64.233.189.104: bytes=32 time=34ms TTL=241 Reply from 64.233.189.104: bytes=32 time=34ms TTL=241 Reply from 64.233.189.104: bytes=32 time=34ms TTL=241 Reply from 64.233.189.104: bytes=32 time=34ms TTL=241 Ping statistics for 64.233.189.104: Packets: Sent = 4, Received = 4, Lost = 0 (0% loss), Approximate round trip times in milli-seconds: Minimum = 34ms, Maximum = 34ms, Average = 34ms

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  • Parsing the output of "uptime" with bash

    - by Keek
    I would like to save the output of the uptime command into a csv file in a Bash script. Since the uptime command has different output formats based on the time since the last reboot I came up with a pretty heavy solution based on case, but there is surely a more elegant way of doing this. uptime output: 8:58AM up 15:12, 1 user, load averages: 0.01, 0.02, 0.00 desired result: 15:12,1 user,0.00 0.02 0.00, current code: case "`uptime | wc -w | awk '{print $1}'`" in #Count the number of words in the uptime output 10) #e.g.: 8:16PM up 2:30, 1 user, load averages: 0.09, 0.05, 0.02 echo -n `uptime | awk '{ print $3 }' | awk '{gsub ( ",","" ) ; print $0 }'`","`uptime | awk '{ print $4,$5 }' | awk '{gsub ( ",","" ) ; print $0 }'`","`uptime | awk '{ print $8,$9,$10 }' | awk '{gsub ( ",","" ) ; print $0 }'`"," ;; 12) #e.g.: 1:41pm up 105 days, 21:46, 2 users, load average: 0.28, 0.28, 0.27 echo -n `uptime | awk '{ print $3,$4,$5 }' | awk '{gsub ( ",","" ) ; print $0 }'`","`uptime | awk '{ print $6,$7 }' | awk '{gsub ( ",","" ) ; print $0 }'`","`uptime | awk '{ print $10,$11,$12 }' | awk '{gsub ( ",","" ) ; print $0 }'`"," ;; 13) #e.g.: 12:55pm up 105 days, 21 hrs, 2 users, load average: 0.26, 0.26, 0.26 echo -n `uptime | awk '{ print $3,$4,$5,$6 }' | awk '{gsub ( ",","" ) ; print $0 }'`","`uptime | awk '{ print $7,$8 }' | awk '{gsub ( ",","" ) ; print $0 }'`","`uptime | awk '{ print $11,$12,$13 }' | awk '{gsub ( ",","" ) ; print $0 }'`"," ;; esac

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  • Nagios NTP, discarding peer

    - by picca
    We're using nagios *check_ntp_time* for monitoring time on our servers. Unfortunately the service is flapping. And reporting a lot of false-positives. It happens everytime for random server in random day time and lasts for ~10-30 minutes. When the problem occurs we get: watch01:~ # /usr/lib/nagios/plugins/check_ntp_time -H lb01 -w 1 -c 2 -v sending request to peer 0 response from peer 0: offset 0.07509887218 sending request to peer 0 response from peer 0: offset 0.07508444786 sending request to peer 0 response from peer 0: offset 0.07499825954 sending request to peer 0 response from peer 0: offset 0.07510817051 discarding peer 0: stratum=0 overall average offset: 0 NTP CRITICAL: Offset unknown| When everything is ok, we get (I used different server to not have to wait): watch01:~ # /usr/lib/nagios/plugins/check_ntp_time -H web02 -w 1 -c 2 -v sending request to peer 0 response from peer 0: offset 0.0002282857895 sending request to peer 0 response from peer 0: offset 0.0002194643021 sending request to peer 0 response from peer 0: offset 0.0002347230911 sending request to peer 0 response from peer 0: offset 0.0002293586731 overall average offset: 0.0002282857895 NTP OK: Offset 0.0002282857895 secs|offset=0.000228s;1.000000;2.000000; We are using: check_ntp_time v1.4.15 (nagios-plugins 1.4.15) on Debian squeeze. Remote ntp daemon is: ntpd - NTP daemon program - Ver. 4.2.4p4 I already found some forums where the problem is described: 1, 2, 3. Every time they edvise to upgrade nagios-plugins, because in version prior to 1.4.13 there was a bug with inserted leap second. But we have already newer version of nagios-plugins.

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  • where is memory gone (no, not buffers or cache)

    - by Marki
    can anyone tell me where the memory is gone: (no, this time neither buffers nor cache) # free total used free shared buffers cached Mem: 3928200 3868560 59640 0 2888 92924 -/+ buffers/cache: 3772748 155452 Swap: 4192956 226352 3966604 top, sorted by memory, descending: top - 13:42:06 up 1 day, 3:47, 2 users, load average: 0.08, 0.12, 0.36 Tasks: 228 total, 1 running, 227 sleeping, 0 stopped, 0 zombie Cpu0 : 2.0%us, 4.0%sy, 0.0%ni, 90.1%id, 0.0%wa, 0.0%hi, 4.0%si, 0.0%st Cpu1 : 0.0%us, 0.0%sy, 0.0%ni, 0.0%id,100.0%wa, 0.0%hi, 0.0%si, 0.0%st Mem: 3928200k total, 3868020k used, 60180k free, 2896k buffers Swap: 4192956k total, 226048k used, 3966908k free, 82068k cached PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 3863 root 20 0 902m 199m 3296 S 7 5.2 99:08.77 ndsd 21906 root 20 0 138m 9076 2988 S 0 0.2 0:00.02 sfcbd 2332 root 20 0 126m 4660 1332 S 0 0.1 0:17.72 mono 4243 wwwrun 20 0 683m 4468 668 S 0 0.1 0:07.38 java 2994 root 20 0 202m 2288 1660 S 0 0.1 6:10.02 httpstkd 4338 root 20 0 184m 2240 1112 S 0 0.1 0:00.52 namcd 21898 root 20 0 32368 1832 1256 R 1 0.0 0:00.08 top In fact, some time ago oom kicked in and crashed the system (kernel panic), and I'm afraid we're again not far from that point.... UPDATE # cat /proc/meminfo MemTotal: 3928200 kB MemFree: 51336 kB Buffers: 2964 kB Cached: 72876 kB SwapCached: 29128 kB Active: 233440 kB Inactive: 88040 kB Active(anon): 188920 kB Inactive(anon): 56752 kB Active(file): 44520 kB Inactive(file): 31288 kB Unevictable: 0 kB Mlocked: 0 kB SwapTotal: 4192956 kB SwapFree: 3966824 kB Dirty: 32 kB Writeback: 0 kB AnonPages: 225112 kB Mapped: 11356 kB Shmem: 32 kB Slab: 1624080 kB SReclaimable: 13740 kB SUnreclaim: 1610340 kB KernelStack: 4176 kB PageTables: 10500 kB NFS_Unstable: 0 kB Bounce: 0 kB WritebackTmp: 0 kB CommitLimit: 6157056 kB Committed_AS: 2397684 kB VmallocTotal: 34359738367 kB VmallocUsed: 441372 kB VmallocChunk: 34359246755 kB HardwareCorrupted: 0 kB HugePages_Total: 0 HugePages_Free: 0 HugePages_Rsvd: 0 HugePages_Surp: 0 Hugepagesize: 2048 kB DirectMap4k: 10240 kB DirectMap2M: 4184064 kB slabtop Active / Total Objects (% used) : 9041019 / 9207548 (98.2%) Active / Total Slabs (% used) : 401132 / 401156 (100.0%) Active / Total Caches (% used) : 91 / 159 (57.2%) Active / Total Size (% used) : 1491537.88K / 1519791.56K (98.1%) Minimum / Average / Maximum Object : 0.02K / 0.17K / 4096.00K OBJS ACTIVE USE OBJ SIZE SLABS OBJ/SLAB CACHE SIZE NAME 4240470 4240319 99% 0.12K 141349 30 565396K pid 2245140 2219675 98% 0.25K 149676 15 598704K size-256 2238090 2210087 98% 0.12K 74603 30 298412K size-128 ...

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  • Strange performance differences in read/write from/to USB flash drive

    - by Mario De Schaepmeester
    When copying files from my 8GB USB 2.0 flash drive with Windows 7 to a traditional hard drive, the average speed is between 25 and 30 MB/s. When doing the reverse, copying to the USB drive, the speed is 5MB/s average. I have tested this with about 4.5GB of files, a mixture of smaller and larger ones. The observations were the same on both FAT32 and exFAT file systems on the USB drive, NTFS on the internal hard disk. I don't think I can be mistaken in saying that flash memory has a lot higher performance than a spinning hard drive in both terms of reading and writing. For both memory types, reading should be faster than writing too. Now I wonder, how can it be that copying files from a fast read memory to a faster write memory is actually slower than copying files from a fast read memory to a slow write memory? I think that the files are stored in RAM before being copied over too, and there's caching as well, but I don't see how even that could tip the balance. It can only be in the advantage of writing to the USB drive, since it is "closer" to the SATA system than the USB port and it will receive data from the internal SATA HDD faster. Perhaps my way of thinking is all wrong or it just depends on the manufacturer of the USB pen. But I am curious.

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  • Xorg eating up too much RAM on Ubuntu 9.10 box

    - by Yang
    Xorg is eating up 444MB of 2GB total RAM on my Ubuntu 9.10 x86_64 machine with nvidia drivers installed for the nvidia G86 (GeForce 8300 GS). top shows: top - 18:21:41 up 6 days, 2:40, 9 users, load average: 0.46, 1.12, 1.22 Tasks: 266 total, 3 running, 262 sleeping, 1 stopped, 0 zombie Cpu(s): 8.4%us, 2.0%sy, 0.0%ni, 89.1%id, 0.5%wa, 0.0%hi, 0.0%si, 0.0%st Mem: 2055736k total, 1965136k used, 90600k free, 3952k buffers Swap: 979924k total, 979908k used, 16k free, 102636k cached PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 1432 root 20 0 1154m 442m 7492 S 8 22.0 32:56.97 Xorg 18462 yang 20 0 1001m 219m 8356 S 0 10.9 5:13.25 chrome 24099 yang 20 0 865m 83m 13m S 0 4.2 0:06.91 chrome xrestop shows: xrestop - Display: :0.0 Monitoring 47 clients. XErrors: 0 Pixmaps: 40430K total, Other: 142K total, All: 40573K total res-base Wins GCs Fnts Pxms Misc Pxm mem Other Total PID Identifier 1c00000 21 46 1 19 697 9128K 18K 9146K 3169 x-nautilus-desktop 1000000 4 3 0 17 194 9000K 4K 9004K 3134 gnome-settings-daemon 1600000 51 2 1 25 1100 7648K 28K 7676K ? compiz For comparison, here's my other Ubuntu box, which also has compiz etc. enabled but with ATI RV370 (Radeon X300SE): top - 18:18:18 up 58 days, 4:27, 9 users, load average: 0.00, 0.00, 0.00 Tasks: 224 total, 1 running, 223 sleeping, 0 stopped, 0 zombie Cpu(s): 0.3%us, 0.3%sy, 0.0%ni, 98.8%id, 0.5%wa, 0.0%hi, 0.0%si, 0.0%st Mem: 1024964k total, 987124k used, 37840k free, 247012k buffers Swap: 2048276k total, 94296k used, 1953980k free, 264744k cached PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 24324 yang 20 0 61936 35m 6364 S 0 3.5 4:35.84 nxagent 1768 ntop 20 0 190m 32m 5388 S 1 3.2 283:36.15 ntop 1178 root 20 0 60588 29m 1788 S 0 3.0 5:48.89 console-kit-dae ... 1315 root 20 0 343m 4956 4020 S 0 0.5 3:43.87 Xorg Any ideas on how to get to the bottom of this? (i.e. not "Log out"/"Reboot") Thanks in advance.

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