On Sat, Mar 28, 2009 at 7:22 PM, Bob Friesenhahn < bfrie...@simple.dallas.tx.us> wrote:
> On Sat, 28 Mar 2009, Michael Shadle wrote: > > Well this is for a home storage array for my dvds and such. If I have to >> turn it off to swap a failed disk it's fine. It does not need to be highly >> available and I do not need extreme performance like a database for example. >> 45mb/sec would even be acceptable. >> > > I can see that 14 disks costs a lot for a home storage array but to you the > data on your home storage array may be just as important as data on some > businesses enterprise storage array. In fact, it may be even more critical > since it seems unlikely that you will have an effective backup system in > place like large businesses do. > > The main problem with raidz1 is that if a disk fails and you replace it, > that if a second disk substantially fails during resilvering (which needs to > successfully read all data on remaining disks) then your ZFS pool (or at > least part of the files) may be toast. The more data which must be read > during resilvering, the higher the probability that there will be a failure. > If 12TB of data needs to be read to resilver a 1TB disk, then that is a lot > of successful reading which needs to go on. > > In order to lessen risk, you can schedule a periodic zfs scrub via a cron > job so that there is less probabily of encountering data which can not be > read. This will not save you from entirely failed disk drives though. > > As far as Tim's post that NOBODY recommends using better than RAID5, I > hardly consider companies like IBM and NetApp to be "NOBODY". Only Sun RAID > hardware seems to lack RAID6, but Sun offers ZFS's raidz2 so it does not > matter. > > I did NOT say nobody recommends using raid5. What I *DID* say was that NOBODY supports using raid-5 and raid-6 under a single pool of storage. Which IBM array are you referring to that is supported with RAID5 and 6 in a single pool? --Tim
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