RE: Reality check for filesystem/disk layout

Can you remind me, what is readahead good for on redo files? I believe that parallelism is much more essential for
the recovery and archiver file is usually quick enough, even without any special tricks.    

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Mladen Gogala
Oracle DBA

-----Original Message-----

Matthew Zito
Sent: Friday, September 26, 2003 3:05 PM To: Multiple recipients of list ORACLE-L  

Avoid small stripe sizes for your redo log volumes - especially on two-disk-only RAID sets, you'll break readahead and write allocation on many arrays.  

Beyond that, it looks good - what kind of array are you using?  

Matt

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Matthew Zito
GridApp Systems
Email: mzito_at_gridapp.com
Cell: 646-220-3551
Phone: 212-358-8211 x 359
http://www.gridapp.com <http://www.gridapp.com/>

-----Original Message-----

JayMiller_at_tdwaterhouse.com
Sent: Friday, September 26, 2003 1:30 PM To: Multiple recipients of list ORACLE-L

We have the luxury of moving a 300G database to a new box that's being built and choosing the specifications, disk layout, striping, etc. After spending the morning poring over Cary Millsap's wonderful VLDB paper this is what we're thinking of but I'd appreciate any comments.  

One of my main goals going in was separating redo logs into 2 sets of disks and archive logs on a third.  

We have 16 disks to play with and seem to be winning the 1+0 battle against some SAs who don't understand why we wouldn't want to use RAID5.  

The database has minimal write activity during the day (other than sorts to the temp tablespace) but huge batch write activity at night and especially at the end of the month (the data load time is enough of a problem that the few partitioned tables we can easily reload are doing unrecoverable loads). There is a lot of read activity during the day, both single row queries from front ends that are rolled out to several thousand people and reports that can do some large sort/merge joins.  

Here's what we were thinking:  

1st Disk Set - 4 72M disks RAID 1+0  

1st and 3rd redo log on outside
Misc. Datafiles in middle
Misc scripts and files used by other departments in center  

2nd Disk Set - 6 72M disks RAID 1+0
Archive logs on outside
Temp tablespace and misc. datafiles in middle Text files used for loading in center  

3rd Disk Set - 6 72M disks RAID 1+0
2nd and 4th redo logs on outside
Rollback tablespace and misc datafiles in middle /oracle (executables and some scripts) in center    

I was debating if there was any advantage in varying stripe sizes across the different disk sets (since I know Cary says redo logs like fine grained stripe sizes) but given the mix of uses for each that doesn't seem viable Received on Fri Sep 26 2003 - 14:24:39 CDT