Yes, that's true, though, I am a bit confused because the Clariion array document I am reading talks about how the write cache can eliminate the RAID5 Write Penalty for sequential and large IOs...resulting in better sequential write performance than RAID10.
anjan -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Sent: Tuesday, August 16, 2005 2:00 PM To: pgsql-performance@postgresql.org Subject: Re: [PERFORM] choosing RAID level for xlogs Quoting Anjan Dave <[EMAIL PROTECTED]>: > Hi, > > > > One simple question. For 125 or more checkpoint segments > (checkpoint_timeout is 600 seconds, shared_buffers are at 21760 or > 170MB) on a very busy database, what is more suitable, a separate 6 disk > RAID5 volume, or a RAID10 volume? Databases will be on separate > spindles. Disks are 36GB 15KRPM, 2Gb Fiber Channel. Performance is > paramount, but I don't want to use RAID0. > RAID10 -- no question. xlog activity is overwhelmingly sequential 8KB writes. In order for RAID5 to perform a write, the host (or controller) needs to perform extra calculations for parity. This turns into latency. RAID10 does not perform those extra calculations. > > > PG7.4.7 on RHAS 4.0 > > > > I can provide more info if needed. > > > > Appreciate some recommendations! > > > > Thanks, > > Anjan > > > > > --- > This email message and any included attachments constitute confidential > and privileged information intended exclusively for the listed > addressee(s). If you are not the intended recipient, please notify > Vantage by immediately telephoning 215-579-8390, extension 1158. In > addition, please reply to this message confirming your receipt of the > same in error. A copy of your email reply can also be sent to > [EMAIL PROTECTED] Please do not disclose, copy, distribute or take > any action in reliance on the contents of this information. Kindly > destroy all copies of this message and any attachments. Any other use of > this email is prohibited. Thank you for your cooperation. For more > information about Vantage, please visit our website at > http://www.vantage.com <http://www.vantage.com/> . > --- > > > > ---------------------------(end of broadcast)--------------------------- TIP 1: if posting/reading through Usenet, please send an appropriate subscribe-nomail command to [EMAIL PROTECTED] so that your message can get through to the mailing list cleanly ---------------------------(end of broadcast)--------------------------- TIP 4: Have you searched our list archives? http://archives.postgresql.org
