Wee Yeh Tan writes: > On 9/5/06, Torrey McMahon <[EMAIL PROTECTED]> wrote: > > This is simply not true. ZFS would protect against the same type of > > errors seen on an individual drive as it would on a pool made of HW raid > > LUN(s). It might be overkill to layer ZFS on top of a LUN that is > > already protected in some way by the devices internal RAID code but it > > does not "make your data susceptible to HW errors caused by the storage > > subsystem's RAID algorithm, and slow down the I/O". > > & Roch's recommendation to leave at least 1 layer of redundancy to ZFS > allows the extension of ZFS's own redundancy features for some truely > remarkable data reliability. > > Perhaps, the question should be how one could mix them to get the best > of both worlds instead of going to either extreme. > > > True, ZFS can't manage past the LUN into the array. Guess what? ZFS > > can't get past the disk drive firmware either....and thats a good thing > > for all parties involved. > > > -- > Just me, > Wire ... > _______________________________________________ > zfs-discuss mailing list > zfs-discuss@opensolaris.org > http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Thinking some more about this. If your requirements does mandate some form of mirroring, then it truly seems that ZFS should take that in charge if only because of the self-healing characteristics. So I feel the storage array's job is to export low latency Luns to ZFS. I'd be happy to live with those simple Luns but I guess some storage will just refuse to export non-protected luns. Now we can definitively take advantage of the Array's capability of exporting highly resilient Luns; RAID-5 seems to fit the bill rather well here. Even an 9+1 luns will be quite resilient and have a low block overhead. So we benefit from the arrays resiliency as well as it's low latency characteristics. And we mirror data at the ZFS level which means great performance and great data integrity and great availability. Note that ZFS write characteristics (all sequential) means that we will commonly be filling full stripes on the luns thus avoiding the partial stripe performance pitfall. If you must shy away from any form of mirroring, then it's either stripe your raid-5 luns (performance edge for those who live dangerously) or raid-z around those raid-5 luns (lower cost, survives lun failures). -r _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
