SQL Server Performance Forum – Threads Archive
Can more then 2 drives be mirrored?(1) Can you mirror (RAID 1) more then 2 drives, not to be confused with a RAID 10.
(2) How do you mirror 4 or more drives?
Our server person said he did not think it was possible to mirror more then 2 drives using hardware mirroring. We have a situation where I would like to use 4 18GB drives for our log files. I always thought 2 was just the minimum number of drives and not the maximum as well. Thanks, Dave
It’s up to your vendor implementation on how to configure more than two drives for a mirror. Any decent vendor should support more than a two-disk mirror, it’s quite common in the industry to have more than a two-disk mirror. I’d be looking for a new vendor if they don’t support that…. As an example, I keep an equal # of tempdb files and spindles in relation to the # of processors in the box. Typically a quad cpu box has a tempdb that consists of four physical files stored on a 4 disk mirror partition (sometimes 8 disks total on high i/o systems).
Thanks. We have mostly Compaq servers so I would assume they support more then two drives in a mirror. Dvae
the Compaq Smart Array controllers have advance RAID levels for multi-disk failure,
but i don’t think it amounts to multi-disk mirroring
SANs have snap shot and mirroring capability, but again i do not think it is for generating more than 2 copies of different set of disks
potentially you could establish a mirror, break it, and then mirror to a different set of disks. why do you really want this?
i suppose you could make 2 RAID pairs in HW, then mirror again in SW, but i think this is stupid (i but actually saw some one make a 2 sets of 3 disk RAID 5, then mirror the pair in the OS, performance stank, and i told him he was stupid, same person who did not know about NIC auto detect and full-duplex, failed to get network backups done). if it would really make you feel better, just mirror 2 drives for the log, but make sure each is in a separate enclosure on separate power sources and SCSI channels.
i think they must be on the same adapter for HW mirror.