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SubjectRe: striping (RAID0) performance ?
On Tue, 23 Jun 1998, Davide Rossetti wrote:

> so, you see a major inprovement in disk seek overlapping, don't you ?

Definately! Then again I use 8k chunks...

Personalities : [1 linear] [2 raid0] [3 raid1] [4 raid5]
read_ahead 128 sectors
md0 : active raid0 sda1 sdb1 4192896 blocks 8k chunks

/dev/sda:
Timing buffered disk reads: 32 MB in 4.86 seconds = 6.58 MB/sec

/dev/sdb:
Timing buffered disk reads: 32 MB in 4.85 seconds = 6.60 MB/sec

/dev/md0:
Timing buffered disk reads: 32 MB in 2.95 seconds =10.85 MB/sec

Attached devices:
Host: scsi0 Channel: 00 Id: 00 Lun: 00
Vendor: SEAGATE Model: ST32550W Rev: 8104
Type: Direct-Access ANSI SCSI revision: 02
Host: scsi0 Channel: 00 Id: 01 Lun: 00
Vendor: SEAGATE Model: ST32550W Rev: 8104
Type: Direct-Access ANSI SCSI revision: 02

> In real life those are not zeroes. they are data from/to our supercomputer
> memories. And in our QCD(Quantum Cromo Dynamics) simulations, there are
> HUGE amount of data to be read/written.

Sounds like fun! You might be better off with chunk size < buffer
size. (just a pseudorandom guess really) Then again is fs even threaded
in 2.0?(can any fs guru verify this) I'm on 2.1.106ac3 using a 2940w
which seems concrete even with SMP+RAID+realtek 8029<g>.

- Chris
--------------------------------------------------------------------------------
Chris Atenasio (chrisa@ultranet.com) -- Friends dont let friends use Windows.
Send me mail with subject "send pgp key" or "word of the day" for autoresponse.



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