Nicolas Williams writes: > 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.
right but in this situation, if the "cosmic ray / bit flip" hits on the way to the controller, the array will store wrong data and we will not be able to reconstruct the correct block. So having multiple I/Os here improves the time to data loss metric. -r > _______________________________________________ > zfs-discuss mailing list > zfs-discuss@opensolaris.org > http://mail.opensolaris.org/mailman/listinfo/zfs-discuss _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
