"Sekajuci" HW RAID (driver DAC960, radic Mylex AcceleRAID)

[Martin 'Megac' Mokry]

Zdrawim ... 

Mam jeden maly problem s RAIDom v serveri.

Konfiguracia servera je asi takato:

Hardware:

 Chipset Intel E7500
 1x Intel XEON 2.00 GHz so zapnutym HT (este jeden socket je volny)
 2x Mylex AcceleRAID 160 LP, na kazdom je 7 SCSI diskov IBM, zbernica
    bezi v rezime "Wide Synchronous at 160 MB/sec"
 2x 512 MB DRAM 

 (dalsie asi nepodstatne veci)
 2x on-board Intel Ethernet Pro 100 
 1x Adaptec AIC-7892B (na nom je len paska)
 1x Altima (nee Broadcom) AC1000 Gigabit Ethernet
 1x ATI Rage XL

Software:
 
 Red Hat Linux 7.3
 Oracle 9.0.1
 Samba 2.2.7

Konfiguracia RAIDu:
 2 diskove polia po 7 diskov, RAID-3, stripe size 64KB, segment size 8KB
 suborovy system je ReiserFS, mount parametre su "defaults,noatime"
 o RAID sa stara ovladac "DAC960"
 
Problem je asi nasledovny:
 Pri citani z RAIDu je prenosova rychlost cca 50 MB/sec, zapis je ale
 velmi pomaly (3-4 MB/sec). Viem ze minimalne v pripade RAID 3 a 5
 rychlost zapisu o dost nizsia ako rychlost citania, ale ma to byt az
 tak rapidne nizsie ? To by vsak nebol ten hlavny problem. Tym je fakt
 ze pri zapise vacsieho mnozstva udajov (niekolko stoviek MB) sa to
 sprava tak ze velmi rychlo prebehne zapis cca 100-200 MB (je jasne ze
 to ide do write-bufferu) a potom sa cely system (presnejsie pristup k
 suborom na tom konkretnom poli) sekne, a po chvilke (asi po uvolneni
 nejakeho dostatocneho miesta vo write-bufferi) zapis pokracuje, dojde k
 naplneniu buffera a situacia sa opakuje. Dost to zneprijemnuje dojem z
 pristupu k udajom na poli napriklad cez sambu. Niekedy kvoli tymto
 "prestavkam" vyhodi Windoze klient chybu. Pomoze prenasanie suborov po
 mensich davkach, je to vsak velmi nepohodlne ...

 Mate niekto skusenosti s prevadzkou RAIDu na tychto radicoch, pripadne
 viete ako by sa dal tento problem vyriesit (napadla ma zmena velkosti
 write buffera na mensiu hodnotu, len neviem ako na to) ? 
 
Za konstruktivne odpovede vopred vdaka ...


PRILOHY:

Obsah /proc/rd/c1/current_status

-- 
Martin Mokry a.k.a. Megac
Work: Vyskumny Ustav Podoznalectva a Ochrany Pody
      (Soil Science and Conservation Research Institute)
      Bratislava, Slovakia
------------- další část ---------------
***** DAC960 RAID Driver Version 2.4.11 of 11 October 2001 *****
Copyright 1998-2001 by Leonard N. Zubkoff <lnz na dandelion.com>
Configuring Mylex AcceleRAID 160 PCI RAID Controller
  Firmware Version: 6.00-15, Channels: 1, Memory Size: 16MB
  PCI Bus: 2, Device: 2, Function: 0, I/O Address: Unassigned
  PCI Address: 0xFD000000 mapped at 0xF8841000, IRQ Channel: 28
  Controller Queue Depth: 512, Maximum Blocks per Command: 2048
  Driver Queue Depth: 511, Scatter/Gather Limit: 128 of 257 Segments
  Physical Devices:
    0:0  Vendor: IBM       Model: IC35L073UWDY10-0  Revision: S21E
         Wide Synchronous at 160 MB/sec
         Serial Number:         E6V0ZJTB
         Disk Status: Online, 143339520 blocks
    0:1  Vendor: IBM       Model: IC35L073UWDY10-0  Revision: S21E
         Wide Synchronous at 160 MB/sec
         Serial Number:         E6V1D9YB
         Disk Status: Online, 143339520 blocks
    0:2  Vendor: IBM       Model: IC35L073UWDY10-0  Revision: S21E
         Wide Synchronous at 160 MB/sec
         Serial Number:         E6V0RKMB
         Disk Status: Online, 143339520 blocks
    0:3  Vendor: IBM       Model: IC35L073UWDY10-0  Revision: S21E
         Wide Synchronous at 160 MB/sec
         Serial Number:         E6V1D5SB
         Disk Status: Online, 143339520 blocks
    0:4  Vendor: IBM       Model: IC35L073UWDY10-0  Revision: S21E
         Wide Synchronous at 160 MB/sec
         Serial Number:         E6V1D7VB
         Disk Status: Online, 143339520 blocks
    0:5  Vendor: IBM       Model: IC35L073UWDY10-0  Revision: S21E
         Wide Synchronous at 160 MB/sec
         Serial Number:         E6V13S5B
         Disk Status: Online, 143339520 blocks
    0:6  Vendor: IBM       Model: IC35L073UWDY10-0  Revision: S21E
         Wide Synchronous at 160 MB/sec
         Serial Number:         E6V0UA6B
         Disk Status: Online, 143339520 blocks
    0:7  Vendor: MYLEX     Model: AcceleRAID 160    Revision: 0600
         Wide Synchronous at 160 MB/sec
         Serial Number:   
  Logical Drives:
    /dev/rd/c1d0: RAID-3, Online, 859963392 blocks
                  Logical Device Initialized, BIOS Geometry: 128/32
                  Stripe Size: 64KB, Segment Size: 8KB
                  Read Cache Disabled, Write Cache Disabled
  No Rebuild or Consistency Check in Progress