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I have a raid5 array /dev/md1, being used as the pv of an LVM Volume Group.
I have a very peculiar problem with the array:
Writes to it happen at 40MB/sec or so.
But *reads* from it happen at 10MB/sec.
This, given how raid5 works, is a bit weird.
dd if=/dev/md1 of=/disks/raid_backup/test_speed bs=10M
gives 21MB/sec, which is, while not good, not bad for dd.
while:
dd if=/dev/mapper/system-raid_lvm of=/disks/raid_backup/test_speed bs=10M
4+0 records in
3+0 records out
31457280 bytes (31 MB) copied, 8.75426 seconds, 3.6 MB/s
which is obviously bogus.
dd if=/dev/sdg of=/disks/raid_lvm/test.speed bs=10M
24+0 records in
23+0 records out
241172480 bytes (241 MB) copied, 11.6211 seconds, 20.8 MB/s
So, writes to the system VG happen at least 4xfaster than reads.
This to me seems insane.
Note that:
pvs
PV VG Fmt Attr PSize PFree
/dev/md0 backup lvm2 a- 1.46T 159.20G
/dev/md1 system lvm2 a- 1.82T 63.04G
/disks/raid_backup/ is actually the backup VG.
/disks/raid_lvm/ is actually the system VG.
Any ideas on why this happens would be very appreciated.
[EMAIL PROTECTED]
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