| From: | Justin Pitts <justinpitts(at)gmail(dot)com> |
|---|---|
| To: | "pgsql-performance(at)postgresql(dot) org" <pgsql-performance(at)postgresql(dot)org> |
| Cc: | Matthew Wakeling <matthew(at)flymine(dot)org>, Pierre C <lists(at)peufeu(dot)com>, Kenneth Cox <kenstir(at)gmail(dot)com>, Scott Marlowe <scott(dot)marlowe(at)gmail(dot)com> |
| Subject: | Re: Advice configuring ServeRAID 8k for performance |
| Date: | 2010-08-06 17:32:18 |
| Message-ID: | AANLkTimsmnqvFmKpKV3hL43+CJsXsPU-bg5eVELOrK7O@mail.gmail.com |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-performance |
>>> As others said, RAID6 is RAID5 + a hot spare.
>>
>> No. RAID6 is NOT RAID5 plus a hot spare.
>
> The original phrase was that RAID 6 was like RAID 5 with a hot spare
> ALREADY BUILT IN.
Built-in, or not - it is neither. It is more than that, actually. RAID
6 is like RAID 5 in that it uses parity for redundancy and pays a
write cost for maintaining those parity blocks, but will maintain data
integrity in the face of 2 simultaneous drive failures.
In terms of storage cost, it IS like paying for RAID5 + a hot spare,
but the protection is better.
A RAID 5 with a hot spare built in could not survive 2 simultaneous
drive failures.
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