matthias platzer wrote: > > hello, > > i saw this thread a bit late, but I had /am having the exact > same issues > on a dual-2-core-cpu opteron box with a 9550SX. (Centos 5 x86_64) > What I did to work around them was basically switching to XFS for > everything except / (3ware say their cards are fast, but only on XFS) > AND using very low nr_requests for every blockdev on the 3ware card. > (like 32 or 64). That will limit the iowait times for the > cpus and make > the 3ware-drives respond faster (see yourself with iostat -x > -m 1 while > benchmarking). > If you can, you could also try _not_ putting the system disks on the > 3ware card, because additionally the 3ware driver/card gives writes > priority. People suggested the unresponsive system behaviour > is because > the cpu hanging in iowait for writing and then reading the system > binaries won't happen till the writes are done, so the > binaries should > be on another io path. > > All this seem to be symptoms of a very complex issue consisting of > kernel bugs/bad drivers/... and they seem to be worst on a AMD/3ware > Combination. > here is another link: > http://bugzilla.kernel.org/show_bug.cgi?id=7372 Actually the real-real fix was to use the 'deadline' or 'noop' scheduler with this card as the default 'cfq' scheduler was designed to work with a single drive and not a multiple drive RAID, so it acts as a govenor on the amount of IO that a single process can send to the device and when you do multiple overlapping IOs performance decreases instead of increases. Personnally I always use 'deadline' as my scheduler of choice. Of course if your drivers are broken that will always negatively impact performance. -Ross ______________________________________________________________________ This e-mail, and any attachments thereto, is intended only for use by the addressee(s) named herein and may contain legally privileged and/or confidential information. If you are not the intended recipient of this e-mail, you are hereby notified that any dissemination, distribution or copying of this e-mail, and any attachments thereto, is strictly prohibited. If you have received this e-mail in error, please immediately notify the sender and permanently delete the original and any copy or printout thereof.