On Wednesday 28 December 2005 22:37, Brad DerManouelian wrote: > On Dec 28, 2005, at 10:30 PM, Yeechang Lee wrote: > > To make a long story short, my 2.8TB JFS-on-LVM2-on-software RAID 5 > > array has certain mysterious performance bottlenecks that result in > > 7.5-10MB/s local write speeds, despite eight spindles and two 3Ware > > 7506 controller cards in JBOD mode and on separate buses and with > > iowait never going above a few percentage points at the very > > most. Over the network that's even slower, of course. > > This actually sounds pretty typical of RAID 5 to me. Every write > results in 2 simultaneous writes. Even slower when you're doing it in > software. Great for redundancy, terrible for throughput. That's the > trade-off.
Erm, software RAID 5 isn't *that* bad. I've got a sw RAID 5 array that only consists of four ATA drives, and can write at a sustained rate of 30MB/s without a problem. I've got a 5-drive U320 software RAID 5 array in another machine that does ~80MB/s without a problem. -- Jarod Wilson [EMAIL PROTECTED]
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