Re: New Disk Setup

From: Noons <>
Date: Tue, 02 Jun 2009 23:04:44 +1000
Message-ID: <h037uk$ut9$>

Mark D Powell wrote,on my timestamp of 29/05/2009 6:15 AM:

> "I've found RAID-5 does work for normal situations"
> I agree, while RAID-5 is not the ideal disk setup for a heavy hitter
> system it is often more than good enough especially since RAID devices
> often have significant write cache as part of their set up.
> When the RAID-5 is done only via the OS with no disk cache then it is
> easier to run into write performance related issues but read is
> generally still decent thinks in large part to the stripping.
> The fact that RAID-5 only protects you from the loss of a single disk
> in the stripe is one reason I suggested two 4 disk stripes rather than
> just a single 8 disk stripe but I have seen places use stripes with
> over 20 disks in them. (If a single disk is likely to fail once in

I'm having a lot of success with RAID5 striped over 8 disks on EMC san. It works very well for our development and test nodes and is a LOT cheaper than the equivalent RAID10 platinum grade!
The way we use this is in a single, vanilla RAID5 striped LUN, then making a single VG in Unix out of the LUN and splitting it into four LVs, no LV striping. Each VG goes into a file system.
First FS - corresponding to outer cylinders on all 8 disks - gets the redo logs. Second FS - the next inner cylinders - gets the undo and temp. Third gets the data+indexes.
Fourth - the innermost and slowest - gets the OS, software and other directories. Works a treat, is cheap and has good performance. Received on Tue Jun 02 2009 - 08:04:44 CDT

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