Messages in this thread | | | Date | Sat, 15 Dec 2001 19:40:32 +0100 | From | Rene Rebe <> | Subject | Re: PDC20265 IDE controller trouble |
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Hi. Thanks for the reply!
I'm sorry tht I can not do many other benchmarks - since the server is in production ...
On Sat, 15 Dec 2001 13:15:57 -0500 (EST) Mark Hahn <hahn@physics.mcmaster.ca> wrote:
> > Single transfer to one disk: > > server1:~ # hdparm -tT /dev/ide/host2/bus0/target0/lun0/disc > > is any of this different if you use non-devfs?
This might make a difference? Maybe the open() call but read/write on a open fd ??
> > Timing buffered disk reads: 64 MB in 2.86 seconds = 22.38 MB/sec > > Timing buffered disk reads: 64 MB in 4.66 seconds = 13.73 MB/sec > > that's somewhat surprising; I wonder if there's some extra > synchronization in the pdc driver. otoh, I didn't notice > this sort of thing at all with a recent raid box I built > (6x100G, 2xpdc, 1 via, athlonxp/1600, pc2100).
Did you tryed ReiserFS on a software raid device?
> can you replicate this with benchmarks more sane than hdparm > (like build a raid0, and run bonnie or iozone on an ext2 on it?)
There is a Raid5 on top of 3 discs running ReiserFS (the performance is bad ...)
But here are the results of a dd if=/bla bla/disc
A single disk: server1:~ # time dd if=/dev/ide/host2/bus0/target0/lun0/part1 of=/dev/zero bs=1000000 count=200 200+0 records in 200+0 records out
real 0m7.106s user 0m0.030s sys 0m3.640s =>28.1 MB/s
And parallel read from two mastess: server1:~ # time dd if=/dev/ide/host2/bus0/target0/lun0/part1 of=/dev/zero bs=1000000 count=200 200+0 records in 200+0 records out
real 0m12.797s user 0m0.010s sys 0m4.210s =>15.6 MB/s
And parallel read from master/slave: server1:~ # time dd if=/dev/ide/host2/bus0/target0/lun0/part1 of=/dev/zero bs=1000000 count=200 200+0 records in 200+0 records out
real 0m18.427s user 0m0.000s sys 0m2.690s =>10.85 MB/s
> > Timing buffered disk reads: 64 MB in 8.36 seconds = 7.66 MB/sec > > that's not particularly surprising, since there's no concurrency > among disks in an ide chain.
I do not understand? No concurrency? The two reads are fighting for the same IDE channel the whole time ... ?
> > Is this an general IDE issue or is some queueing code in the kernel > > rather bad/slow for this task??? > > hdparm is a fairly horrible benchmark; running two at once is nonsense. > and hdparm's use of block devices probably interacts with things like > the blocksize (1k unless you build a 4k FS), and the fact that blkdev > moved into the pagecache.
OK. Above are some raw-read numbers. Currently the disc are in a RAID5 setup with ReiserFS on top - running in production ...
The ReiserFS is realy realy realy slow (reported in another thread). We might add a 4th disc an reconfigure it leaving some Gigs on each disc for tests - but not in this year ...
k33p h4ck1n6 René
-- René Rebe (Registered Linux user: #248718 <http://counter.li.org>)
eMail: rene.rebe@gmx.net rene@rocklinux.org
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