RE: Ocr and Voting disk - slow disk
- From: "Matthew Zito" <mzito@xxxxxxxxxxx>
- To: <Jon.Crisler@xxxxxxx>, <tinojam@xxxxxxxxx>, <oracle-l@xxxxxxxxxxxxx>
- Date: Thu, 10 Sep 2009 13:54:28 -0400
I took a quick look at one of my Linux RAC clusters that happens to be
nothing more than a CRS and an ASM instance:
su9-rac011-01:/app/oracle/crs/10.2.0/bin # ./ocrdump -stdout -keyname
SYSTEM.css.diskfile
09/10/2009 13:47:24
./ocrdump.bin -stdout -keyname SYSTEM.css.diskfile
[SYSTEM.css.diskfile]
ORATEXT : /dev/sdb1
su9-rac011-01:/app/oracle/crs/10.2.0/bin # iostat -x 1 sdb | grep sdb
Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s rkB/s wkB/s
avgrq-sz avgqu-sz await svctm %util
sdb 1.12 0.01 2.12 1.26 5.46 3.07 2.73 1.53
2.53 0.00 1.21 1.04 0.35
sdb 0.00 0.00 2.08 1.04 2.08 1.04 1.04 0.52
1.00 0.01 4.33 4.33 1.35
sdb 0.00 0.00 2.15 1.08 2.15 1.08 1.08 0.54
1.00 0.00 0.33 0.33 0.11
sdb 0.00 0.00 2.25 1.12 2.25 1.12 1.12 0.56
1.00 0.00 0.33 0.33 0.11
sdb 0.00 0.00 2.04 1.02 2.04 1.02 1.02 0.51
1.00 0.01 3.33 3.33 1.02
sdb 0.00 0.00 2.25 1.12 2.25 1.12 1.12 0.56
1.00 0.00 0.33 0.33 0.11
sdb 0.00 0.00 2.25 1.12 2.25 1.12 1.12 0.56
1.00 0.00 0.33 0.33 0.11
I believe there are other partitions on that disk that are part of an
ASM diskgroup that's not in use, so certainly at a worst case your
voting disk does 1kb/sec/node of reads and writes.
Also, since it's very very small, it's likely those couple blocks that
are getting modified just stay in cache all the time. I wouldn't be
concerned about the performance.
Matt
> -----Original Message-----
> From: oracle-l-bounce@xxxxxxxxxxxxx
[mailto:oracle-l-bounce@xxxxxxxxxxxxx]
> On Behalf Of Crisler, Jon
> Sent: Thursday, September 10, 2009 1:08 PM
> To: tinojam@xxxxxxxxx; oracle-l@xxxxxxxxxxxxx
> Subject: RE: Ocr and Voting disk - slow disk
>
> I would not consider those slow- maybe medium speed perhaps.
Certainly
> slower than 15k and 18k disks but not slow. It also depends on the
> connection method (SAN, FC, Scsi etc.) and cache.
>
> In my experience, the OCR is not hit that hard, and its usually pretty
> small. Perhaps 150mb is the biggest I have seen. The voting disk is
> even smaller; I have not looked at I/O rates on the voting disk but
they
> seem lightweight based on a brief look.
>
> If your trying to put these on a slower device while reserving faster
> devices for data, I think this is a good tradeoff. I might be able to
> get some performance data to firm up my opinion.
>
> -----Original Message-----
> From: oracle-l-bounce@xxxxxxxxxxxxx
> [mailto:oracle-l-bounce@xxxxxxxxxxxxx] On Behalf Of Paul Barrett
> Sent: Thursday, September 10, 2009 12:02 PM
> To: oracle-l@xxxxxxxxxxxxx
> Subject: Ocr and Voting disk - slow disk
>
>
> -------------------------------------
> From: Paul Barrett<tinojam@xxxxxxxxx>
> To: oracle-l@xxxxxxxxxxxxx;
> Subject: Ocr and Voting disk - slow disk
> Date: Sep 10, 8:32 AM
>
> Is it advisable to put the ocr and voting disks on slow disks - 10,000
> RPM fiber channel disks? What is the ramifications in doing this? Has
> anyone placed the ocr and voting disk on this speed disk and have you
> encounterd any node eviction problems with this configuration?
>
> Sent on the go from my Peek
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