Hardware isn't very good I believe, and it's about 2-3 years old, but the RAID is Linux software, and though not very good the difference between reading and writing should probably be greater... (?)
Would you set 512Kb readahead on both drives and RAID? I tried various configurations and none seemed to make a big difference. It seemed correct to me to set 512kb per drive and 1024kb for md0. A Dimecres 30 Maig 2007 16:09, Luke Lonergan va escriure: > This sounds like a bad RAID controller - are you using a built-in hardware > RAID? If so, you will likely want to use Linux software RAID instead. > > Also - you might want to try a 512KB readahead - I've found that is optimal > for RAID1 on some RAID controllers. > > - Luke > > On 5/30/07 2:35 AM, "Albert Cervera Areny" <[EMAIL PROTECTED]> wrote: > > Hi, > > after doing the "dd" tests for a server we have at work I obtained: > > Read: 47.20 Mb/s > > Write: 39.82 Mb/s > > Some days ago read performance was around 20Mb/s due to no readahead in > > md0 so I modified it using hdparm. However, it seems to me that being it > > a RAID1 read speed could be much better. These are SATA disks with 3Gb of > > RAM so I did 'time bash -c "dd if=/dev/zero of=bigfile bs=8k count=786432 > > && sync"'. File system is ext3 (if read many times in the list that XFS > > is faster), but I don't want to change the file system right now. > > Modifing the readahead from the current 1024k to 2048k doesn't make any > > difference. Are there any other tweaks I can make? > > > > > > ---------------------------(end of broadcast)--------------------------- > > TIP 4: Have you searched our list archives? > > > > http://archives.postgresql.org > > ---------------------------(end of broadcast)--------------------------- > TIP 6: explain analyze is your friend -- Albert Cervera Areny Dept. Informàtica Sedifa, S.L. Av. Can Bordoll, 149 08202 - Sabadell (Barcelona) Tel. 93 715 51 11 Fax. 93 715 51 12 ==================================================================== ........................ AVISO LEGAL ............................ La presente comunicación y sus anexos tiene como destinatario la persona a la que va dirigida, por lo que si usted lo recibe por error debe notificarlo al remitente y eliminarlo de su sistema, no pudiendo utilizarlo, total o parcialmente, para ningún fin. Su contenido puede tener información confidencial o protegida legalmente y únicamente expresa la opinión del remitente. El uso del correo electrónico vía Internet no permite asegurar ni la confidencialidad de los mensajes ni su correcta recepción. En el caso de que el destinatario no consintiera la utilización del correo electrónico, deberá ponerlo en nuestro conocimiento inmediatamente. ==================================================================== ........................... DISCLAIMER ............................. This message and its attachments are intended exclusively for the named addressee. If you receive this message in error, please immediately delete it from your system and notify the sender. You may not use this message or any part of it for any purpose. The message may contain information that is confidential or protected by law, and any opinions expressed are those of the individual sender. Internet e-mail guarantees neither the confidentiality nor the proper receipt of the message sent. If the addressee of this message does not consent to the use of internet e-mail, please inform us inmmediately. ==================================================================== ---------------------------(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
