On Thu, 1 Apr 1999, Val Bercovici (NetApp) wrote:
What are results with minra=off? Wouldn't that be a better setting for large sequential files?
Yeah, it definitely is.... I'm getting peaks of almost 15MB/sec disk reads with three clients over three 100tx ports reading three different 256MB files. sysstat reports ~55% CPU usage at that point. Reading all files out of cache gets me close to 24MB/sec (at roughly the same CPU usage).
Is the disk bandwidth limited because of parity calculations on reads? I just realized that RAID literature seems to concentrate on disk write performance hits with a parity system, but it would be reasonable that a RAID will calculate and compare parity for reads as well. That would explain the upper limit on sequential read throughput.
I agree, this seems slow. How many disks in that volume/raid group in question? Could that file somehow be very fragmented?
5x9GB drives, tests were done on a mostly empty filesystem with 3x256MB and 4x64MB files laid down sequentially (no other write activity in between).
Reading the same file from cache is faster, but still not close to what I'd expect over an otherwise quiet 100 Mbps link.
Can't agree with you here. You're getting roughly 8.4 MB/s over link capable of about 10-12.5 MB/s max. Not optimal, but not bad either...
I'm also quite willing to believe that Solaris 2.6 doesn't have the fastest NFS client code either... my FreeBSD box accessing the same Netapp over a switched 100t LAN manages to sustain 9200K/sec. ;-)