[Problem disappeared in new kernel] Bad SSD performance

Question

Hello all, I'm an ex-gentoo user turned arch. Looking forward to it!
Anyway, I have a brand new OCZ Vertex SSD -- theoretical 230MB/s read times. In the livecd installer, hdparm gets 210MB/s reads, pretty awesome. However, in my current installation, I am only getting 75MB/s.
My kernel is 2.6.29, the livecd has 2.6.28. I checked, UDMA/133 is enabled on my drive. I (and some generous IRC users) have absolutely no idea what's happening here.
Any help would be appreciated!
[root@wakka jake]# hdparm -i /dev/sda
/dev/sda:
Model=OCZ-VERTEX, FwRev=1370, SerialNo=92M9W154QY80YY06496G
Config={ HardSect NotMFM HdSw>15uSec Fixed DTR>10Mbs RotSpdTol>.5% }
RawCHS=16383/16/63, TrkSize=0, SectSize=0, ECCbytes=12288
BuffType=unknown, BuffSize=32767kB, MaxMultSect=16, MultSect=16
CurCHS=16383/16/63, CurSects=16514064, LBA=yes, LBAsects=62533296
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 *udma6
AdvancedPM=no WriteCache=enabled
Drive conforms to: Unspecified: ATA/ATAPI-5,6,7
Last edited by wakkadojo (2009-06-17 13:40:38)

Answer 1

I have been all over google and many other forums, there's really nothing on this. I'm almost certain it's an Arch linux problem of some sort.
I just gave your suggestion a shot. Here's what we get:
# hdparm -t -W 0 /dev/sda
/dev/sda:
setting drive write-caching to 0 (off)
write-caching = 1 (on)
Timing buffered disk reads: 220 MB in 3.02 seconds = 72.96 MB/sec
So no improvement -- but then again it says it turns off write caching when it really does not.
However, I would like to point out that it is probably not write caching that is causing this slowdown, since on the livecd write caching is enabled, and others have not posted anything about disabling write caching to improve ssd performance.
Last edited by wakkadojo (2009-05-31 23:55:24)