Nicolas Williams wrote:
On Thu, Jan 25, 2007 at 10:57:17AM +0800, Wee Yeh Tan wrote:
On 1/25/07, Bryan Cantrill <[EMAIL PROTECTED]> wrote:
...
after all, what was ZFS going to do with that expensive but useless
hardware RAID controller? ...
I almost rolled over reading this.
This is exactly what I went through when we moved our database server
out from Vx** to ZFS. We had a 3510 and were thinking how best to
configure the RAID. In the end, we ripped out the controller board
and used the 3510 as a JBOD directly attached to the server. My DBA
was so happy with this setup (especially with the snapshot capability)
he is asking for another such setup.
The only benefit of using a HW RAID controller with ZFS is that it
reduces the I/O that the host needs to do, but the trade off is that ZFS
cannot do combinatorial parity reconstruction so that it could only
detect errors, not correct them. It would be cool if the host could
offload the RAID I/O to a HW controller but still be able to read the
individual stripes to perform combinatorial parity reconstruction.
OK, not the *only* benefit :-) IMHO, the most visible benefit is the
nonvolatile write cache. The RAID configuration is simply an implementation
detail.
-- richard
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