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-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Darke, Clive wrote: > > Try running sar (system activity reporter) for the period in question. > My guess is that paging/swapping will be peaking. Do you have enough > swap space? Good idea - also note that the Debian sar (sysstat package) will automatically store data for later review as it sets up the relevant cron jobs for sar. The sa1 manual page usually describes how to do this. The routine cron jobs that kill performance worst in my experience are the big "find" and "update" which do a lot of disk IO. IDE disk performance under GNU/Linux can get really stupid defaults, so it is worth checking it if you see any performance issues at all. Found one of our boxes at work wasn't using DMA the other day, after a power outage it was reporting 6 hours to synchronise the mirrored IDE drives, and really killing the performance through excessive interrupts. It didn't matter it doesn't do IO in routine use, but not having the disks mirrored for six hours after a power glitch is not good. A quick fiddle with "hdparm" (In Debian package hdparm) and a ten fold increase in IO performance later... Basically you do something like "hdparm -tT /dev/hda". Of course people need some idea of what is normal/good/insane. hdparm is not really intended for SCSI disks, but my desktop which has some wacky hardware in says; hdparm -tT /dev/sda1 /dev/sda1: Timing cached reads: 3224 MB in 2.00 seconds = 1612.24 MB/sec Timing buffered disk reads: 122 MB in 3.06 seconds = 39.86 MB/sec I'd expect "Timing buffered disk reads" to give 10MB/sec with very old IDE disks, 20MB/s with old disks/buses, and with very new stuff almost anything is possible. Less that 10MB/sec suggests that the disk drive isn't being used efficiently, usually due to lack of DMA, which can be enabled at boot by adding "hdparm" with options to the start up. Now as for "Timing cached reads" I've no idea what is sensible. -----BEGIN PGP SIGNATURE----- Comment: Encryption...is a powerful defensive weapon for free people. Comment: Using GnuPG with Thunderbird - http://enigmail.mozdev.org iD8DBQFCtUhZGFXfHI9FVgYRAgOjAJ9s2u5ceiSFZ0xRTQ7t0EklBgjIfwCg13bx U0NTxsvITRyMlg8R1QcT9LY= =7Ylh -----END PGP SIGNATURE----- -- The Mailing List for the Devon & Cornwall LUG Mail majordomo@xxxxxxxxxxxxx with "unsubscribe list" in the message body to unsubscribe. FAQ: www.dcglug.org.uk/linux_adm/list-faq.html