50% speed penalty for LVM on mdraid
David Nielsen
david at lovesunix.net
Sun Mar 18 18:39:22 UTC 2007
søn, 18 03 2007 kl. 17:59 +0000, skrev Andy Burns:
> > Wow that explains a lot.. performance on Development has be awful for me
> > lately and I have been unable to figure out why, this might be related.
> >
> > My setup is 2 400GB drives in RAID0 using dmraid with LVM ontop.
>
> It's a while since it tried dmraid instead of mdraid, does it use a
> UUID as the PV name for /dev/mapper? I suppose pvdisplay would show,
> then you could try hdparm on the PV under LVM compared to the LV above
> it.
/dev/mapper/VolGroup00-LogVol00:
Timing cached reads: 1050 MB in 2.00 seconds = 524.68 MB/sec
HDIO_DRIVE_CMD(null) (wait for flush complete) failed: Inappropriate
ioctl for device
Timing buffered disk reads: 162 MB in 3.01 seconds = 53.84 MB/sec
HDIO_DRIVE_CMD(null) (wait for flush complete) failed: Inappropriate
ioctl for device
/dev/mapper/nvidia_bbgdbcgj:
Timing cached reads: 1142 MB in 2.00 seconds = 571.12 MB/sec
HDIO_DRIVE_CMD(null) (wait for flush complete) failed: Inappropriate
ioctl for device
Timing buffered disk reads: 300 MB in 3.00 seconds = 99.97 MB/sec
HDIO_DRIVE_CMD(null) (wait for flush complete) failed: Inappropriate
ioctl for device
/dev/sda:
Timing cached reads: 1096 MB in 2.00 seconds = 547.65 MB/sec
Timing buffered disk reads: 182 MB in 3.00 seconds = 60.61 MB/sec
Yep something odd is definitely going on.
--
"Ridicule is the only weapon that can be used against unintelligible
propositions. Ideas must be distinct before reason can act upon them.”
-Thomas Jefferson
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