50% speed penalty for LVM on mdraid

[David Nielsen]

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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