Robin Bowes wrote:
Bill Davidsen wrote:
There have been several recent threads on the list regarding software
RAID-5 performance. The reference might be updated to reflect the poor
write performance of RAID-5 until/unless significant tuning is done.
Read that as tuning obscure parameters and throwing a lot of memory into
stripe cache. The reasons for hardware RAID should include "performance
of RAID-5 writes is usually much better than software RAID-5 with
default tuning.
Could you point me at a source of documentation describing how to
perform such tuning?
No. There has been a lot of discussion of this topic on this list, and a
trip through the archives of the last 60 days or so will let you pull
out a number of tuning tips which allow very good performance. My
concern was writing large blocks of data, 1MB per write, to RAID-5, and
didn't involve the overhead of small blocks at all, that leads through
other code and behavior.
I suppose while it's fresh in my mind I should write a script to rerun
the whole write test suite and generate some graphs, lists of
parameters, etc. If you are writing a LOT of data, you may find that
tuning the dirty_* parameters will result in better system response,
perhaps at the cost of some small total write throughput, although I
didn't notice anything significant when I tried them.
Specifically, I have 8x500GB WD STAT drives on a Supermicro PCI-X 8-port
SATA card configured as a single RAID6 array (~3TB available space)
No hot spare(s)?
--
bill davidsen <davidsen@xxxxxxx>
CTO TMR Associates, Inc
Doing interesting things with small computers since 1979
-
To unsubscribe from this list: send the line "unsubscribe linux-raid" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
