Quoting "John G. Heim" <[email protected]>: > Has anyone configured a database server with RAID-5?
Sure... Most people don't, but some workloads might benefit from it. > Is it really a bad idea > to do so? Depends on your workload... If it is a mostly read-intensive database, it would be fine. It it is a mostly write-intensive database, it would most likely be very bad, unless you have a very light load. > But is it better to do RAID-1 or RAID-5. I can't I recommend RAID-10 for the database files. You can do multiple raid levels for different disks (system on raid-1, DB on raid-10, etc). > figure out why RAID-1 would be better than RAID-5. I understand that with > RAID-5, a single database write might translate into writing 2 blocks (a > data block and a parity block). But doesn't RAID-1 *always* do an extra > write for every data block written? RAID-1 always does a write to both disks, so it is slow writing. But it can then read from either or both disks, so it is up to twice as fast as a single disk. RAID-5 is slow because it has to split the data into N pieces, calculate the parity, then write out N+1 writes (1 each to N+1 disks). But because it writes the N+1 in parallel, and reads the N in parallel, it is rather fast especially at reads... RAID-10 does a combination (split and stripe across disks similar to RAID-5, but at the same time mirror it like RAID-1 across stripes). It is the most robust version (as far as disk loss goes), and is often the fastest, though as always that depends on your workload and your setup. You could use any of the RAID levels 1, 5, 6, or 10... Which is _best_ depends on your budget and your workload... To properly set this up, you need to know your workload... How much data? Mostly read or mostly write or a good read/write mix? Large data requests or small data requests? Stuff like that can have a big impact on which disk layout is best... -- Eric Rostetter The Department of Physics The University of Texas at Austin Go Longhorns! _______________________________________________ Linux-PowerEdge mailing list [email protected] https://lists.us.dell.com/mailman/listinfo/linux-poweredge Please read the FAQ at http://lists.us.dell.com/faq
