| From: | david(at)lang(dot)hm |
|---|---|
| To: | Mark Mielke <mark(at)mark(dot)mielke(dot)cc> |
| Cc: | Florian Weimer <fw(at)deneb(dot)enyo(dot)de>, Fernando Hevia <fhevia(at)ip-tel(dot)com(dot)ar>, "'pgsql-performance'" <pgsql-performance(at)postgresql(dot)org> |
| Subject: | Re: With 4 disks should I go for RAID 5 or RAID 10 |
| Date: | 2007-12-26 23:05:50 |
| Message-ID: | Pine.LNX.4.64.0712261504310.11785@asgard.lang.hm |
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| Thread: | |
| Lists: | pgsql-performance |
On Wed, 26 Dec 2007, Mark Mielke wrote:
> Florian Weimer wrote:
>>> seek/read/calculate/seek/write since the drive moves on after the
>>> read), when you read you must read _all_ drives in the set to check
>>> the data integrity.
>>>
>> I don't know of any RAID implementation that performs consistency
>> checking on each read operation. 8-(
>>
>
> Dave had too much egg nog... :-)
>
> Yep - checking consistency on read would eliminate the performance benefits
> of RAID under any redundant configuration.
except for raid0, raid is primarily a reliability benifit, any performance
benifit is incidental, not the primary purpose.
that said, I have heard of raid1 setups where it only reads off of one of
the drives, but I have not heard of higher raid levels doing so.
David Lang
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