|
Dobrica Pavlinušić's random unstructured stuff
Disk performance: Revision 8
{toc: }
Have many disks. More disk spindles brings more than capacity alone! (Same as in databases) ^ Speed ^^ Individial disks Slow laptop 2.5" 5400 disk .pre dpavlin@llin:~$ sudo hdparm -i /dev/sda /dev/sda: Model=FUJITSU MHV2080BH , FwRev=00840028, SerialNo= NW05T6B29HM5 Config={ HardSect NotMFM HdSw>15uSec Fixed DTR>10Mbs } RawCHS=16383/16/63, TrkSize=0, SectSize=0, ECCbytes=4 BuffType=DualPortCache, BuffSize=8192kB, MaxMultSect=16, MultSect=?16? CurCHS=16383/16/63, CurSects=16514064, LBA=yes, LBAsects=156301488 IORDY=on/off, tPIO={min:240,w/IORDY:120}, tDMA={min:120,rec:120} PIO modes: pio0 pio1 pio2 pio3 pio4 DMA modes: mdma0 mdma1 mdma2 UDMA modes: udma0 udma1 udma2 udma3 udma4 *udma5 AdvancedPM=yes: mode=0x80 (128) WriteCache=enabled Drive conforms to: unknown: ATA/ATAPI-3,4,5,6,7 * signifies the current active mode dpavlin@llin:~$ sudo hdparm -tT /dev/sda /dev/sda: Timing cached reads: 1566 MB in 2.00 seconds = 782.85 MB/sec Timing buffered disk reads: 66 MB in 3.03 seconds = 21.79 MB/sec .pre Interesting numbers are `BuffSize` (cache in disk) and `MaxMultSect` which we want to use for read-ahead param: .pre hdparm -m 16 -a 16 /dev/sda .pre This will *decrease* a bit speed of linerar buffer reads which `hdparm` uses, but we will pull from disk only blocks which are allready in cache, improving random read/write performance. To find optimal readahead for your drive using hdparm access pattern you can use "hdparm-readahead.pl"<http://svn.rot13.org/index.cgi/scripts/view/trunk/hdparm-readahead.pl> which will try different combinations for you. Faster (!) external 3.5 USB disk (no `hdparm -i` on USB), but just because it's *another* disk not loaded by system. .pre dpavlin@llin:~$ sudo hdparm -tT /dev/sdb /dev/sdb: Timing cached reads: 1508 MB in 2.00 seconds = 753.72 MB/sec Timing buffered disk reads: 56 MB in 3.03 seconds = 18.48 MB/sec .pre ^^ Software RAID {include: [Home-made RAID disk holder]} Drive info: .pre dpavlin@brr:~$ sudo hdparm -i /dev/sdd /dev/sdd: Model=WDC WD5000AAKS-00YGA0 , FwRev=12.01C02, SerialNo= WD-WCAS80929678 Config={ HardSect NotMFM HdSw>15uSec SpinMotCtl Fixed DTR>5Mbs FmtGapReq } RawCHS=16383/16/63, TrkSize=0, SectSize=0, ECCbytes=50 BuffType=unknown, BuffSize=16384kB, MaxMultSect=16, MultSect=?16? CurCHS=16383/16/63, CurSects=16514064, LBA=yes, LBAsects=976773168 IORDY=on/off, tPIO={min:120,w/IORDY:120}, tDMA={min:120,rec:120} PIO modes: pio0 pio3 pio4 DMA modes: mdma0 mdma1 mdma2 UDMA modes: udma0 udma1 udma2 udma3 udma4 udma5 *udma6 AdvancedPM=no WriteCache=enabled Drive conforms to: Unspecified: ATA/ATAPI-1,2,3,4,5,6,7 * signifies the current active mode .pre Speed of individual drives in array: .pre dpavlin@brr:~$ sudo hdparm -tT /dev/sda /dev/sdb /dev/sdd /dev/sda: Timing cached reads: 1982 MB in 2.00 seconds = 991.18 MB/sec Timing buffered disk reads: 232 MB in 3.03 seconds = 76.67 MB/sec /dev/sdb: Timing cached reads: 2010 MB in 2.00 seconds = 1004.95 MB/sec Timing buffered disk reads: 228 MB in 3.01 seconds = 75.85 MB/sec /dev/sdd: Timing cached reads: 2006 MB in 2.00 seconds = 1003.01 MB/sec Timing buffered disk reads: 230 MB in 3.01 seconds = 76.47 MB/sec .pre How are hey assembled into /dev/md0 RAID 5 array: .pre dpavlin@brr:~$ cat /proc/mdstat Personalities : [raid6] [raid5] [raid4] md0 : active raid5 sdd1[0] sda1[2] sdb1[1] 976767872 blocks level 5, 64k chunk, algorithm 2 [3/3] [UUU] .pre Speed of array .pre dpavlin@brr:~$ sudo hdparm -tT /dev/md0 /dev/md0: Timing cached reads: 1986 MB in 2.00 seconds = 993.20 MB/sec Timing buffered disk reads: 434 MB in 3.01 seconds = 144.41 MB/sec .pre As expected RAID 5 speed is 75 + 75 + 0 (parity disk) ~ 144 MB/sec ^ Temperature Disks don't like it hot! .pre root@brr:~# hddtemp /dev/sda /dev/sdb /dev/sdd /dev/sda: WDC WD5000AAKS-00YGA0: 33°C /dev/sdb: WDC WD5000AAKS-00YGA0: 32°C /dev/sdd: WDC WD5000AAKS-00YGA0: 32°C .pre On output above, middle disk is `/dev/sda` so it's 1° hotter than other two. I could mitigate this with additional fan on front of case, but it's making enough noise already, so I'll leave it as is. ^ Data security ^^ Smart .pre root@brr:~# smartctl --all /dev/sda | head -20 smartctl version 5.38 [i686-pc-linux-gnu] Copyright (C) 2002-8 Bruce Allen Home page is http://smartmontools.sourceforge.net/ === START OF INFORMATION SECTION === Model Family: Western Digital Caviar Second Generation Serial ATA family Device Model: WDC WD5000AAKS-00YGA0 Serial Number: WD-WCAS80815866 Firmware Version: 12.01C02 User Capacity: 500,107,862,016 bytes Device is: In smartctl database [for details use: -P show] ATA Version is: 8 ATA Standard is: Exact ATA specification draft version not indicated Local Time is: Sat Oct 11 00:27:01 2008 CEST SMART support is: Available - device has SMART capability. SMART support is: Enabled === START OF READ SMART DATA SECTION === SMART overall-health self-assessment test result: PASSED .pre Before you start to beleve in SMART as solution to all disk health problems, read "Failure Trends in a Large Disk Drive Population"<http://labs.google.com/papers/disk_failures.pdf> http://media.arstechnica.com/staff.media/failurehd.png ^^ RAID Also interesting is "Some RAID Issues"<http://etbe.coker.com.au/2008/10/14/some-raid-issues/> |