Hello,
We want to combine two HW RAID controllers with RAID 0 using MD and see
some performance issues.
Setup:
- Linux 2.6.16-64 bit, Dual XEON, 1 GB RAM
- 2 RAID controllers: ARECA with 7 SATA disks each (RAID5)
- SW RAID 0 over the two HW RAID controllers
- stripe size is always 64k
Measured with IOMETER (MB/s, 64 kb block size with sequential I/O).
one HW RAID controller:
- R: 360 W: 240
two HW RAID controllers:
- R: 619 W: 480 (one IOMETER worker per device)
MD0 over two HW RAID controllers:
- R 367 W: 433 (one IOMETER worker over md device)
Read throughput is similar to a single controller. Any hint how to
improve that?
Using a larger block size does not help.
We are considering using MD to combine HW RAID controllers with battery
backup support for better data protection. In this scenario md should do
no write caching. Is it possible to use something like O_DIRECT with md?
Regards,
Mirko
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