Nico Morrison <nico.morrison@micronicos.com> wrote:
>
> Hello Folks,
>
> We have 2 (identical hardware) busy public 2U rack servers, both have
> several hundred users & peak email (for example) deliveries at 300/5min
> during the daytime.
>
> Both servers run RAID1 over 2 EIDE disk drives.
>
> One server is fine - it never has problems - it is running RH7.3 and CPU
> loads are normal.
>
> The other server has constant disk activity & kjournald at CPU load of
> 50/60/70% most of the time! this machine is running RH7.2
>
> The same processes & loads are on both machines - can anyone tell me why one
> machine should have so much kjournald activity & the other not?
>
> Is it a difference between 7.2 & 7.3 or must it be another factor?
Usually, this is due to IDE drives running in PIO mode and not DMA mode.
> How can I find out?
>
Look at the output of `hdparm -i':
# hdparm -i /dev/hda
/dev/hda:
Model=Maxtor 5T040H4, FwRev=TAH71DP0, SerialNo=T4J0N9BC
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=80043264
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: 1 2 3 4 5 6
See the "*" next to UDMA2? This disk is doing DMA.
You can manually force DMA mode, which is considered risky. Or upgrade the
kernel, perhaps.
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