disk IO request queue 2005-08-05 - By nasvel
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Magnus Andersen wrote:
>This sounds very similar to what I experienced when I went live on a
>RHEL 3 / 9i environment. A couple of questions.
>
>1. How are the Oracle share mounted to the system?
>
>
For oracle, we've got 4 harddisk attached to a controller SCSI. We have
a big tablespace which is composed of 16 dbf files. And the 16 files is
spreading out on the first 3 disks, and the last disk we use to store
the index tablespace.
>2. Have you played with Linux vm?
>
>
We've tuned the shmmax and max open files. And we're not lack of memory,
there is 6G cached memory.
[mrtg@(protected) mrtg]$ free
total used free shared buffers cached
Mem: 16167632 16105196 62436 0 189340 6684672
-/+ buffers/cache: 9231184 6936448
Swap: 4194160 1196604 2997556
>3. Are you using hugetlb?
>
>
no, because hugetlb is not available in AS2.1. But in AS2.1 the bigpages
is enabled. According oracle, there is no big diff between them. You
think it's important?
http://www.oracle.com/technology/pub/notes/technote_rhel3.html
Enterprise Linux 3 has replaced bigpages with a feature called hugetlb,
a backport of what is also in Linux kernel 2.6. There are a few
differences in how hugetlb works. Hugetlb behavior is similar to that of
bigpages; the pages are backed by large TLB entries, are not pageable,
and are preallocated, which means that once you allocate x megabytes of
hugetlb pages, that amount of physical memory can be used only through
hugetlbfs or shm allocated with SHM_HUGETLB.
Thank you very much!
dux
>On 8/5/05, nasvel <nasvel@(protected)> wrote:
>
>
>>Hi,
>>
>>since some weeks our database server (redhat taroon + oracle 9i)
>>suffered from a very bad performance. The load avg climbed sometimes to
>>80% :(, althought I think I've a powerful machine (HP, 3 Intel Xeon with
>>16G memory).
>>
>>To try to find out the problem, I looked at the iostat report. I found
>>the await time are pretty high, and the average queue length is about
>>10. Someone told me that it is normal for a DB server, but I have some
>>doubt, so I would like to have you guy's opinions about that...
>>
>>any suggestion is welcome, thanks
>>
>>dux
>>
>>=== begin output ===
>>
>> Linux 2.4.9-e.62enterprise 05.08.2005
>>
>>cpu-moy: %user %nice %sys %idle
>> 17,63 0,02 12,31 70,04
>>
>>Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s avgrq-sz avgqu-sz
>>await svctm %util
>>cciss/c1d1p1
>> 889,26 11,04 515,44 13,11 623,61 193,26 1,55 10,62
>>21,30 8,03 42,42
>>cciss/c1d0p1
>> 273,76 45,13 100,64 48,85 872,20 751,95 10,86 10,62
>>114,52 26,39 39,45
>>cciss/c1d2p1
>> 198,26 108,73 107,90 27,83 326,31 1061,51 10,22 10,62
>>100,75 26,34 35,76
>>cciss/c1d3p1
>> 233,38 29,04 89,97 30,70 463,79 477,95 7,80 8,29
>>68,69 26,78 32,32
>>
>>=== end output ===
>>
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>>
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>>
>
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