Hello Peter, Thursday, January 11, 2007, 1:08:38 AM, you wrote:
>> It's just a common sense advise - for many users keeping raidz groups >> below 9 disks should give good enough performance. However if someone >> creates raidz group of 48 disks he/she probable expects also >> performance and in general raid-z wouldn't offer one. PS> There is at least one reason for wanting more drives in the same PS> raidz/raid5/etc: redundancy. PS> Suppose you have 18 drives. Having two raidz:s constisting of 9 drives is PS> going to mean you are more likaly to fail than having a single raidz2 PS> consisting of 18 drives, since in the former case yes - two drives can go PS> down, but only if they are the *right* two drives. In the latter case any two PS> drives can go down. PS> The ZFS administration guide mentions this recommendation, but does not give PS> any hint as to why. A reader may assume/believe it's just general adviced, PS> based on someone's opinion that with more than 9 drives, the statistical PS> probability of failure is too high for raidz (or raid5). It's a shame the PS> statement in the guide is not further qualified to actually explain that PS> there is a concrete issue at play. I don't know if ZFS MAN pages should teach people about RAID. If somebody doesn't understand RAID basics then some kind of tool where you just specify pool of disk and have to choose from: space efficient, performance, non-redundant and that's it - all the rest will be hidden. -- 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
