Re: How to improve db performance with $7K? - Mailing list pgsql-performance

From Greg Stark
Subject Re: How to improve db performance with $7K?
Date
Msg-id 873btokkoh.fsf@stark.xeocode.com
Whole thread Raw
In response to Re: How to improve db performance with $7K?  (Jacques Caron <jc@directinfos.com>)
List pgsql-performance
Jacques Caron <jc@directinfos.com> writes:

> When writing:
> - in RAID 0, 1 drive
> - in RAID 1, RAID 0+1 or 1+0, 2 drives
> - in RAID 5, you need to read on all drives and write on 2.

Actually RAID 5 only really needs to read from two drives. The existing parity
block and the block you're replacing. It just xors the old block, the new
block, and the existing parity block to generate the new parity block.

--
greg

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