We just got a Seagate ST15150N 4GB disk added to our
AlphaServer 2100 and have been disappointed with its
performance. We expected it to be faster than our
RZ28 disks since it spins at 7200 rpm, but when testing
it with a C program that just writes out data as fast
as possible and times it, we got a 1.9 MB/sec write
rate on the Seagate. I remembered reading someone's
posting that showed how to use the dd utility to send
data directly to the raw disk device. By using that
method, I was able to get the write rate up to 5.8
MB/sec by using an output block size of 1/2 MB. With a
block size of 8192 bytes, I got close to the 1.9 MB/sec
I was seeing before. So, it appears to me that the
performance is being reduced because the ADVFS wants to
write to the disk in 8192 byte chunks. Does anyone
know if it's possible to increase the output block size
used by ADVFS? This would improve performance on the
RZ28 disks also.
Received on Wed May 31 1995 - 15:15:50 NZST