On Thursday November 9 2006 7:04 am, Carlos E. R. wrote:
The Thursday 2006-11-09 at 12:01 +0700, Fajar Priyanto wrote:
Software RAID level 5 is slower than 1 harddisk? Partly true. Writing performance is a bit slower since it must calculate the parity. Reading speed is good.
But write operations are distributed over the three disks and parallelized, so it should be faster.
Carlos E. R.
Not. RAID5 has to first write the data, then it has to calculate the parity, then it writes the parity. It can't do all three in parallel. It has to actually write the data portion so it has the necessary information to calculate the parity and then write the parity. RAID5 write performance sucks. RAID5 read performance can be faster than a single hard drive due to more data actually being in cache somewhere and not having to do a physical I/O to a drive. Stan