Re: [gentoo-user] software raid performance (was:optimum disk performance)

[HvR]

see below...

On Thu, 2003-10-30 at 10:49, Alan wrote:

On Thu, Oct 30, 2003 at 04:17:45PM +0200, Craig Main wrote:
> Hi all,
[..]

Figured I'd chime in here with my own question.  I have software RAID0
set up on my / partition across hda and hdb, should the throughput of
the raid on /dev/md0 be basically double the throughput of the
individual disk? 

IE: 

phoenix warez # hdparm -tT /dev/hda /dev/hdb /dev/md0
 
/dev/hda:
 Timing buffer-cache reads:   1652 MB in  2.00 seconds = 826.00 MB/sec
 Timing buffered disk reads:   84 MB in  3.03 seconds =  27.72 MB/sec
 
/dev/hdb:
 Timing buffer-cache reads:   1664 MB in  2.00 seconds = 832.00 MB/sec
 Timing buffered disk reads:   94 MB in  3.03 seconds =  31.02 MB/sec
 
/dev/md0:
 Timing buffer-cache reads:   1652 MB in  2.00 seconds = 826.00 MB/sec
 Timing buffered disk reads:  136 MB in  3.03 seconds =  44.88 MB/sec

with mdo striped over hda and hdb the best you can do is 27+31 for speed, but then only if each disk is on its own IDE controller (so not hanging of the same cable), if you want 100mb then you have to buy more disks and stripe them, or go to scsi

Shouldn't /dev/md0 be a bit faster, basically 50-60MB/sec?  My drives 
and raid config look like the following, any suggestions on getting
100MB/sec like another poster here with RAID0 would be appreciated :)

I'd guess it's either overhead or I don't have the proper 133 cables on
my drives (pretty sure I do though) or something like that.  This is on 
an A7N8X-DX board with IDE hard drives, agpgart with nvidia support 
built into the kernel, dma on by default in the kernel.  

phoenix warez # cat /etc/raidtab
raiddev         /dev/md0
        raid-level              0
        nr-raid-disks           2
        nr-spare-disks          0
        persistent-superblock   1
        chunk-size              32
        device                  /dev/hdb1
        raid-disk               0
        device                  /dev/hda6
        raid-disk               1

phoenix warez # hdparm -i /dev/hda /dev/hdb
 
/dev/hda:
 
 Model=Maxtor 54098H8, FwRev=DAC10SC0, SerialNo=K80JJDFC
 Config={ Fixed }
 RawCHS=16383/16/63, TrkSize=0, SectSize=0, ECCbytes=57
 BuffType=DualPortCache, BuffSize=2048kB, MaxMultSect=16, MultSect=16
 CurCHS=16383/16/63, CurSects=16514064, LBA=yes, LBAsects=80041248
 IORDY=on/off, tPIO={min:120,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: disabled (255) WriteCache=enabled
 Drive conforms to: ATA/ATAPI-6 T13 1410D revision 0:
 
 * signifies the current active mode
 

/dev/hdb:
 
 Model=Maxtor 52049H3, FwRev=JAC61HU0, SerialNo=F3H0HWFC
 Config={ Fixed }
 RawCHS=16383/16/63, TrkSize=0, SectSize=0, ECCbytes=57
 BuffType=DualPortCache, BuffSize=2048kB, MaxMultSect=16, MultSect=16
 CurCHS=16383/16/63, CurSects=16514064, LBA=yes, LBAsects=40021632
 IORDY=on/off, tPIO={min:120,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: disabled (255) WriteCache=enabled
 Drive conforms to: ATA/ATAPI-6 T13 1410D revision 0:
 
 * signifies the current active mode


phoenix warez # hdparm /dev/hda /dev/hdb
 
/dev/hda:
 multcount    = 16 (on)
 IO_support   =  1 (32-bit)
 unmaskirq    =  1 (on)
 using_dma    =  1 (on)
 keepsettings =  1 (on)
 readonly     =  0 (off)
 readahead    = 255 (on)
 geometry     = 4982/255/63, sectors = 80041248, start = 0
 
/dev/hdb:
 multcount    = 16 (on)
 IO_support   =  1 (32-bit)
 unmaskirq    =  1 (on)
 using_dma    =  1 (on)
 keepsettings =  1 (on)
 readonly     =  0 (off)
 readahead    = 255 (on)
 geometry     = 39704/16/63, sectors = 40021632, start = 0

Any hints appreciated.

alan