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RE: Sun T4 Storage Arrray and BAARF

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Date: Thu, 4 Aug 2005 13:11:46 -0700
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It cannot be calculated because it is a new system. It can only be estimated by talking to the researchers. Much of the data will be geospatial. Where the heck is that photon? I have not worked with geospatial data before. I expect tha RAID 5 will be okay. Data collected will not be prone to updates.  

Again except for hash joins I haven't seen much of a RAID 5 penalty. We have systems which record over 15,000 inserts per second. But then there is only one input stream.  


From: Allen, Brandon [] Sent: Thu 8/4/2005 11:37 AM
To: MacGregor, Ian A.; ORACLE-L
Subject: RE: Sun T4 Storage Arrray and BAARF

It takes at least 4 disks to implement RAID 1+0. RAID 1+0 means you are mirroring (1) and striping (0), so you have two mirrored pairs (2 x 2) that your data is striped across. If you are only using two disks, then they are only RAID1 or RAID0 - not RAID10.

My experiences would support that RAID 5 is okay as long as you are doing 90%+ reads - but beware of the times when your application's I/O pattern changes or you have to do occasional loads, batch jobs, etc. with heavy writes - RAID 5 is horrible when it comes to writes. If you have a lot of cache, you may be able to mask the problem though - that seems to be the trend from the SAN sales folks - RAID5 with massive cache. We had a problem on one of our arrays where we found that when one disk went out, the cache was automatically disabled for the entire array - performance was horrible for 2 days until we figured out what had happened.

You should be able to easily calculate your read/write ratio - just look in v$sysstat for 'physical reads' and 'physical writes'.


-----Original Message-----
[]On Behalf Of MacGregor, Ian A.

. . .

Due to space requirements, I've always divided a Storedge array thus: Two disks, total as a RAID 10

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I don't know the distribution of reads and writes.

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Received on Thu Aug 04 2005 - 15:15:09 CDT

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