Hello Peter, Wednesday, June 28, 2006, 11:24:32 PM, you wrote:
PT> Robert, >> PT> You really need some level of redundancy if you're using HW raid. >> PT> Using plain stripes is downright dangerous. 0+1 vs 1+0 and all >> PT> that. Seems to me that the simplest way to go is to use zfs to mirror >> PT> HW raid5, preferably with the HW raid5 LUNs being completely >> PT> independent disks attached to completely independent controllers >> PT> with no components or datapaths in common. >> >> well, it will give you less than half your raw storage. >> Due to costs I belive in most cases it won't be acceptable. >> People are using raid-5 mostly due to costs and you are proposing >> something worse (in terms of available logical storage) than >> mirroring. PT> I realise that, but the question was about what combination of PT> ZFS redundancy and HW-raid redundancy made sense. My point was PT> that putting no redundancy at all at the HW-raid layer was a PT> really bad idea, and the self-healing capability of zfs means PT> that you want a level of redundancy within zfs. So you are PT> inevitably going to lose some extra capacity. Which is better - PT> zfs raidz on hardware mirrors, or zfs mirror on hardware raid-5? PT> I wouldn't rule out raidz (or even raidz2) across multiple PT> arrays that are HW-raid5 internally. My real concern there is PT> the small random read performance issue. I hit that problem (raidz on hw-raid5) with lot of small random reads (and many small writes). The performance was not acceptable here (nor more raid-z groups due to too much logical storage consumed for redundancy). I belive that in many cases mirroring hw-raid-5 luns would perform actually better. And why exactly do you think that not redundant luns on hw arrays is a bad idea? (except lack of hot spare support in zfs) You still would benefit from caches in the array. -- Best regards, Robert mailto:[EMAIL PROTECTED] http://milek.blogspot.com _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
