topic Re: EVA8100: Oracle DBA question in Disk Enclosures

EVA8100: Oracle DBA question

Michael T. Slack — Wed, 11 May 2011 11:55:17 GMT

pasted question from Oracle DBA
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The Database services group has a requirement to tune the Oracle initialization parameter: "db_file_multiblock_read_count".

To accomplish this goal, it is believed one should tune the parameter to match the number or multiple of the number of blocks the HP - EVA typically works with.

How many blocks does the HP - EVA fetch from disk on a single fetch? Is there an optimal number of blocks that the HP - EVA processes within it's cache when attempting to fulfill a read request?
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If you can help answer the specific question, that would be great. In the meantime, I am seeking out Oracle/EVA tuning whitepapers.

Thanks,
Mike

Re: EVA8100: Oracle DBA question

Uwe Zessin — Wed, 11 May 2011 12:42:37 GMT

The EVA's internal chunk-size is 128KB -
that is 256 x 512-byte blocks.

Re: EVA8100: Oracle DBA question

SUBHAJIT KHANBARMAN_1 — Wed, 11 May 2011 13:09:20 GMT

1 Vdisk RSTORE =
---------------------

VRAID-> 0
PSEG-> 4
DATA-> 4
SIZE-> 8MB
CHUNK-> 64KB
-------------------------

VRAID-> 5
PSEG-> 4+1
DATA-> 4
SIZE-> 10MB
CHUNK-> 80 KB
--------------------------

VRAID-> 1
PSEG-> 4+4
DATA-> 4
SIZE-> 16MB
CHUNK-> 128KB

Now I hope you will be implementing VRAID 1 for Oracle database so go for 128KB.

Re: EVA8100: Oracle DBA question

Michael T. Slack — Wed, 11 May 2011 15:02:09 GMT

Thank you for the quick responses!

Re: EVA8100: Oracle DBA question

Oscar_Maimó — Thu, 12 May 2011 12:09:27 GMT

I believed that EVA chunk size was always the same (128K) regardless RAID type. I was wrong...???
Greetings
Oscar

Re: EVA8100: Oracle DBA question

Uwe Zessin — Thu, 12 May 2011 12:12:33 GMT

I agree with you...
"CHUNK" seams to mean something completely different and RSTOREs and PSEGs are completely irrelevant for the question.

Re: EVA8100: Oracle DBA question

SUBHAJIT KHANBARMAN_1 — Thu, 12 May 2011 12:35:17 GMT

I am sorry about the post.

Chunk size is 128KB (256 blocks X 512 bytes) fixed.

1 PSEG = 16 chunk
1 chunk size = 128KB
1 PSEG size = (16 X 128) = 2 MB