Ross Vandegrift wrote:
On Sat, Jan 14, 2006 at 01:40:53AM -0500, Mark Hahn wrote:
Initially, we were getting 'hdparm -t' numbers around 80MB/s, but this
was when we were testing /dev/sdb1 - the (only) partition on the device.
When we started testing /dev/sdb, it increased significantly to around
180MB/s. I'm not sure what to conclude from this.
there are some funny interactions between partitions, filesystems
and low-level parameters like readahead.
Hmmm, I'm not convinced, though it could be that the disks in my
workstation are not fast enough.
I used hdparm and your iorate program to compare the performance on my
fastest disk (7200rpm, ATA100). The difference between partition vs.
disk is definitely within the margin of error: 2-3MB/sec when I'm
averaging around 50MB/sec.
I'd be suspicious of much more difference between the two...
In which case, I'm suspicious - using 'hdparm -t' on h/w RAID0 (4 disks) :
/dev/sdb:
Timing buffered disk reads: 536 MB in 3.00 seconds = 178.57 MB/sec
/dev/sdb1:
Timing buffered disk reads: 100 MB in 3.01 seconds = 33.19 MB/sec
That's a big difference in my book.
However, with bonnie++, using filesystems created on the above devices,
I get similar numbers :
/dev/sdb:
--Sequential Input--
-Per Chr- --Block--
K/sec %CP K/sec %CP
38586 76 126818 15
/dev/sdb1:
--Sequential Input-
-Per Chr- --Block--
K/sec %CP K/sec %CP
38185 76 127569 15
After running that, I reran hdparm, and it reported ~40MB for *both*
/dev/sdb and /dev/sdb1.
Then I unmount /dev/sdb and it's back up to 155MB/s !?!?!
It's not making any sense to me :(
Strange. I guess I should just ignore 'hdparm -t'?
Max.
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