Hi! 2010/9/23 Gary Mills <mi...@cc.umanitoba.ca> > > On Tue, Sep 21, 2010 at 05:48:09PM +0200, Alexander Skwar wrote: > > > > We're using ZFS via iSCSI on a S10U8 system. As the ZFS Best > > Practices Guide http://j.mp/zfs-bp states, it's advisable to use > > redundancy (ie. RAIDZ, mirroring or whatnot), even if the underlying > > storage does its own RAID thing. > > > > Now, our storage does RaID and the storage people say, it is > > impossible to have it export iSCSI devices which have no redundancy/ > > RAID. > > If you have a reliable Iscsi SAN and a reliable storage device, you > don't need the additional redundancy provided by ZFS.
Okay. This contradicts the ZFS Best Practices Guide, which states: # For production environments, configure ZFS so that # it can repair data inconsistencies. Use ZFS redundancy, # such as RAIDZ, RAIDZ-2, RAIDZ-3, mirror, or copies > 1, # regardless of the RAID level implemented on the # underlying storage device. With such redundancy, faults in the # underlying storage device or its connections to the host can # be discovered and repaired by ZFS. > > > Actually, were would there be a difference? I mean, those iSCSI > > devices anyway don't represent real disks/spindles, but it's just > > some sort of abstractation. So, if they'd give me 3x400 GB compared > > to 1200 GB in one huge lump like they do now, it could be, that > > those would use the same spots on the real hard drives. > > Suppose they gave you two huge lumps of storage from the SAN, and you > mirrored them with ZFS. What would you do if ZFS reported that one of > its two disks had failed and needed to be replaced? You can't do disk > management with ZFS in this situation anyway because those aren't real > disks. Disk management all has to be done on the SAN storage device. Yes. I was rather thinking about RAIDZ instead of mirroring. Anyway. Without redundancy, ZFS cannot do recovery, can it? As far as I understand, it could detect block level corruption, even if there's not redundancy. But it could not correct such a corruption. Or is that a wrong understanding? If I got the gist of what you wrote, it boils down to how reliable the SAN is? But also SANs could have "block level" corruption, no? I'm a bit confused, because of the (perceived?) contra- diction to the Best Practices Guide… :) Best regards, Alexander -- ↯ Lifestream (Twitter, Blog, …) ↣ http://alexs77.soup.io/ ↯ ↯ Chat (Jabber/Google Talk) ↣ a.sk...@gmail.com , AIM: alexws77 ↯ _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
