Hi,
I have a setup with 15 SATA drives configured as 3 x SW RAID with 5
drives each with 64k stripe size. Configuration: kernel version is
2.6.18-8.1.3.el5, CPU Xeon 5130, LSI PCI-X SAS controller.
I am testing the devices in parallel with seq I/O using Oracle Orion and
1 MB block size.
3 x MD RAID 5 (all values in MB/s):
Read: 800.42
Write: 564.75
When I setup a volume group + lv on each of the three devices I get the
following results:
Read: 729.28 (-9 %)
Write: 362.30 (- 36 %)
Is there a reason that write performance is so much slower?
---
Striping: I would like to aggregate the individual RAID into a single vg
with a lv using all disks.
Using md with RAID 0 over 3 x RAID 5 I get the following results (stripe
size is 256k):
Read: 700.68
Write: 530.43
When using LVM to do the striping (-i 3 -I 256K) I get the following:
Read: 660.71 (- 6%)
Write: 149.29 (- 72%)
Should one avoid LVM striping or are there some parameters that need to
be adjusted?
Regards,
Mirko
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