Asset ID:	1-71-1006112.1
Update Date:	2009-09-23
Keywords:

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Solution Type  Technical Instruction Sure

Solution  1006112.1 :   Mirrored Sun StorEdge[TM] T3 arrays: Creating Oracle[R] datafiles is slow  


PreviouslyPublishedAs
208561

Description
Cache settings on Sun StorEdge[TM] T3 arrays can increase time taken to
create Oracle[R] datafiles. The issue described below, could affect a variety
of write-intensive workloads.


Steps to Follow
When using mirrored Sun StorEdge T3 arrays with different cache policies
(one writebehind, one writethrough), creating Oracle datafiles can be 3 times
slower than breaking the mirror, and only using the T3 array, with writebehind
enabled.

This is because software mirroring will work at the rate of the slowest writer,
which, in the above case will be the T3 array, with writethrough cache policy.

The reason is, that the software device driver responsible for mirroring,
waits for writes to complete to both devices, before it tells the Operating
System that the write is complete. Waiting for both writes to complete, aids
the availablility of data in the event of a hardware failure.

The above is common to mirroring in both Solaris[TM] Operating System,
using one of the following:

          Solstice DiskSuite[TM] software,
Online: DiskSuite[TM] software,
Solaris[TM] Volume Manager software,

and also in VERITAS Volume manager (VxVM).

Current configuration guidelines and best practices can be found at

http://www.sun.com/solutions/blueprints/1001/t3bp.pdf

The current status of a Sun StorEdge T3 array's cache policy, can be
checked by connecting to the array, and issuing the 'vol mode' command,
as below:-

t3-ds-gmp02:/:<3>vol mode

volume        mounted    cache         mirror
vol01         yes        writebehind   off

Product
Sun StorageTek T3 Array

Internal Comments
For internal Sun use only.

See also Problem Resolution <Document: 1011886.1> for issue relating to T3 cache settings and data

integrity

VOSJEC, t3, T3, purple, cache, writethrough, writebehind, oracle, datafile, data file, performance, vxvm, mirror, sds, ods, lvm
Previously Published As
74555
Product_uuid
2a6d7d50-0a18-11d6-8e0b-f0bd33b24928|Sun StorageTek T3 Array

Change History
Date: 2007-05-25
User Name: 31620
Action: Modify Tech Group
Comment:
Moved to new Tech Group to allow migration to IBIS
Andy - Admin Modify of Tech Group to Storage
Version: 0
Date: 2004-08-24
User Name: 18392
Action: Approved
Comment: Did some trademarking, added some formatting to preserve the command output format.
Version: 2
Date: 2004-08-24
User Name: 18392
Action: Accept
Comment:
Version: 0

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