Re: Hardware for PG
От | Adrian 'Dagurashibanipal' von Bidder |
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Тема | Re: Hardware for PG |
Дата | |
Msg-id | 1026460506.8453.64.camel@atlas обсуждение исходный текст |
Ответ на | Re: Hardware for PG ("Joshua D. Drake" <jd@commandprompt.com>) |
Список | pgsql-general |
On Thu, 2002-07-11 at 18:37, Joshua D. Drake wrote: > Hello, > > Ahhh that is not true. RAID 5 is much, much faster than a mirror (RAID > 1). I believe you are thinking about mirrored + striped which is RAID10 > (also know as 1+0). That is faster than RAID 5 but requires 4 disks > where RAID 5 requires 3. I'd be careful with such general statements. RAID5 may be much faster than mirroring when reading, especially as the number of disks increases. But with RAID5 writing is usually slower (a typical one-stripe-size write requires at least 2 blocks to be read and written again, hitting 2 disks 2 twice. Only n-1-stripe-size writes (where n = # of disks in the array) can be done without reading first). And, btw, RAID10 and RAID 1+0 is not necessarily the same. Depending on the vendor, one is a striped set of mirrored disks, the other a mirrored set of striped disks. RAID 0+1 is also sometimes used to mean the same thing (one or the other). cheers -- vbi -- secure email with gpg http://fortytwo.ch/gpg
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