topic Storage issue in Operating System - Linux

Storage issue

Pierguido — Thu, 08 Nov 2007 13:17:53 GMT

Hi.
I have here a HP ML150 with a sata raid card E200 with BBWC and 4 500GB hd in raid5.
I noticed a very poor performance writing on the disk...i get max 21mbit/s.
I use ext3 over lvm volumes.
With the same setup on an old PIV and no raid i get 40mbit/s.
What's wrong? I use debian etch and kernel 2.6.23.1.
I tried also with different kernels.
Thank you

Pier

Re: Storage issue

Ivan Ferreira — Thu, 08 Nov 2007 13:28:59 GMT

>>> With the same setup on an old PIV and no raid i get 40mbit/s.

What kind of disk?

SATA disks are not the fastest disks, and with RAID 5, you could get worst performance than single disk, because of parity calculation.

What is the speed when you "read" from the disk?

Are you doing the exactly same performance test? Is the system idle?

Re: Storage issue

Steven E. Protter — Thu, 08 Nov 2007 13:37:59 GMT

Shalom Pier,

I have to agree that more information is needed.

I'd like to know what kind of applications are being run on it. For example an oracle or mysql database with a lot of write activity needs storage to be raid 1. However a mostly read data mine can be raid 5 without difficulty.

The devil may be in the details of the applications, memory settings, database configuration issues (ex oracle SGA) and such.

If your figure is off a network transfer, then network configuration could be a factor.

SEP

Re: Storage issue

Pierguido — Fri, 09 Nov 2007 04:42:01 GMT

Here more details:

the server is doing actually nothing as it's a test server.
i made a bonnie++ test and i got these results:

------Sequential Output------
-Per Chr- --Block-- -Rewrite-
K/sec %CP K/sec %CP K/sec
19284 43 19476 5 12608

--Sequential Input- --Random-
-Per Chr- --Block-- --Seeks--
%CP K/sec %CP K/sec %CP /sec %CP
3 36597 74 88286 12 532.4 0

here a dd output:

srv-cluster-1:/home/pier# dd if=/dev/zero of=pppp.img bs=1024 count=3000000
3000000+0 records in
3000000+0 records out
3072000000 bytes (3.1 GB) copied, 149.703 seconds, 20.5 MB/s

These are the result with a file server with 7 500GB hd raid 5 (with different raid card, a 3ware card):

------Sequential Output------
-Per Chr- --Block-- -Rewrite-
K/sec %CP K/sec %CP K/sec %CP
53830 98 177074 34 32281 5

--Sequential Input- --Random-
-Per Chr- --Block-- --Seeks--
K/sec %CP K/sec %CP /sec %CP
22564 42 51874 3 350.8 0

dd output:

srv-file:/home/pier# dd if=/dev/zero of=pppp.img bs=1024 count=3000000
3000000+0 records in
3000000+0 records out
3072000000 bytes (3.1 GB) copied, 17.538 seconds, 175 MB/s

I mean, i don't expect that hp card to be as fast as the other, but at least give me some decent performance.
The result from the old PIV, are from a normal ide disk i think 40GB big (so pretty old).

Pier