David Mathog wrote: > I'm hoping somebody has seen this before and can suggest what might be > going on. > > One machine (Arima HDAMA-I board, dual Opteron 280, 4GB RAM, > Sil 3114 Sata controller, Sil 5.4.03 firmware) has mysteriously slow > SATA IO. This is the case for two different disks (WD10EARS and > ST340014AS), two different disk schedulers, and two different OS's > (Mandriva 2010.0 and PLD 2.97 rescue linux.) Using a different brand of > cable, and plugging into a different SATA port didn't help either. > However, move those disks to another machine (Asus A8N5X, Nvidia CK804 > SATA controller, single core, 1 GB RAM, Knoppix) and they are both much > faster. Raw results from various experiments here: > > http://saf.bio.caltech.edu/pub/pickup/bonnie++.rtf > http://saf.bio.caltech.edu/pub/pickup/sustained_write.rtf > > For the sustained write test both disks on the slow system take about > 102s to write 4GB to disk, or around 41.3GB/s. That isn't horrible > horrible, but it isn't great either. On the faster machine the WD10EARS > does the job in 39 seconds, and even the old Seagate is done in 74s. It > strikes me that something must be rate limiting both disks to about the > same throughput. The Sil 3114 chip is somehow interfaced through the > PCI bus, but even if that is only 33MHz it is still 4 bytes wide and > should be able to handle around 132 MB/s, 3X what I'm seeing. All of > the PCI and PCI-X slots are unoccupied. I have no previous experience > with the Sil 3114 or the Arima board, so don't know if this is typical > for either. > > Perhaps the oddest part of this is that during these tests the disk > light on the slow system blinks but is often off for long periods. > Conversely, on the faster system the disk light stays on pretty > steadily. As if on the slower system it is doing something else when it > should be doing disk IO.
As mentioned to David in a separate post, I see similar (worse) performance deltas using an S-I controller. I see the same delta using sata_sil driving an ATI SB4xx south bridge. It might be kernel related, as escalated here: https://bugzilla.redhat.com/show_bug.cgi?id=502499 -- Geoffrey D. Jacobs _______________________________________________ Beowulf mailing list, [email protected] sponsored by Penguin Computing To change your subscription (digest mode or unsubscribe) visit http://www.beowulf.org/mailman/listinfo/beowulf
