Messages in this thread | | | Date | Thu, 27 Jan 2011 10:40:31 -0500 (EST) | From | Justin Piszcz <> | Subject | Re: xfs: very slow after mount, very slow at umount |
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On Thu, 27 Jan 2011, Mark Lord wrote:
> On 11-01-27 12:30 AM, Stan Hoeppner wrote: >> Mark Lord put forth on 1/26/2011 9:49 PM: >> >>> agcount=7453 >> >> That's probably a bit high Mark, and very possibly the cause of your problems. >> :) Unless the disk array backing this filesystem has something like 400-800 >> striped disk drives. You said it's a single 2TB drive right? >> >> The default agcount for a single drive filesystem is 4 allocation groups. For >> mdraid (of any number of disks/configuration) it's 16 allocation groups. >> >> Why/how did you end up with 7452 allocation groups? That can definitely cause >> some performance issues due to massively excessive head seeking, and possibly >> all manner of weirdness. > > This is great info, exactly the kind of feedback I was hoping for! > > The filesystem is about a year old now, and I probably used agsize=nnnnn > when creating it or something. > > So if this resulted in what you consider to be many MANY too MANY ags, > then I can imagine the first new file write wanting to go out and read > in all of the ag data to determine the "best fit" or something. > Which might explain some of the delay. > > Once I get the new 2TB drive, I'll re-run mkfs.xfs and then copy everything > over onto a fresh xfs filesystem. > > Can you recommend a good set of mkfs.xfs parameters to suit the characteristics > of this system? Eg. Only a few thousand active inodes, and nearly all files are > in the 600MB -> 20GB size range. The usage pattern it must handle is up to > six concurrent streaming writes at the same time as up to three streaming reads, > with no significant delays permitted on the reads. > > That's the kind of workload that I find XFS handles nicely, > and EXT4 has given me trouble with in the past. > > Thanks
Hi Mark,
I did a load of benchmarks a long time ago testing every mkfs.xfs option there was, and I found that most of the time (if not all), the defaults were the best.
Justin.
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