topic Re: sar and VA7400 in Disk Enclosures

sar and VA7400

Holcova Jarmila — Fri, 30 May 2003 08:48:55 GMT

How relevant the sar output is for logical disk (LUN) of VA7400 array?
sar -d
device %busy avque r+w/s blks/s avwait avserv
c3t0d5 90.82 0.50 231 9147 5.07 5.72
c3t0d5 92.19 0.50 242 10063 5.07 6.00
c3t0d5 91.74 0.50 230 9289 5.06 5.98
c3t0d5 90.65 0.50 237 10567 5.08 5.76
sar -u
00:00:00 %usr %sys %wio %idle
10:20:00 50 13 31 6
10:40:00 44 12 38 6
11:00:00 42 12 39 6
11:20:00 44 12 40 4
11:40:00 42 13 39 6
12:00:01 47 9 38 6
12:20:01 54 11 31 4
Thanks for ideas
Jarka

Re: sar and VA7400

Massimo Bianchi — Fri, 30 May 2003 09:01:45 GMT

Hi,
usually is quite accurate.

I see the disk have a very high % busy, and therefore your system has high %wio.

Usually %wio must be less than 10% on a weel tuned system.

You are trasferring about 5Mb/s, and it's not much for a VA, may be you are doing work on may small files.

Your system is pretty busy with user and system%... are your application tuned well ?

To get accurate stats i use

sar -d 3 100
, to sample every 3 seconds and not to interfere too much with work.

HTH,
Massimo

Re: sar and VA7400

Eugeny Brychkov — Fri, 30 May 2003 09:21:46 GMT

Jakra,
'sar' measures storage perfomance at the host side. To have whole picture how VA performs use CommandView 'armperf' command to view whole array or LUN-specific perfomance data. This utility generates comma-delimited formatted file, thus you can import it to excel
Eugeny

Re: sar and VA7400

Holcova Jarmila — Fri, 30 May 2003 10:57:48 GMT

Thanks for responses.
I think AutoRaid VA7400 works ok, disks are equally loaded only I cannot interpret armperf metrics Command Latency.
Does the value avque=0.50 mean that array is able to process requests without long waiting even if %busy is 90?
Should I rather concentrate on tuning application?
Thank you both.
Jarka

Re: sar and VA7400

Massimo Bianchi — Fri, 30 May 2003 11:18:19 GMT

Hi,
i think avque is AVerage QUEue, so a value of 0,5 if O.K., no request are queued for later service, even if your disk are 90% busy.

It might be a problem if you avque gets up to higher values.

Massimo