Re: [Jfs-discussion] Fragmentation and poor write speeds.
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From: Jason F. <jas...@gm...> - 2007-01-28 07:01:21
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I ended up deleting enough to copy the rest elsewhere and start over. I'm using ext3 for the time being, as it can shrink (and subsequently let me replace it with another filesystem if necessary) -- but my speeds are back up to 130MB/sec+, where they should be. I still have jfs and my / and /home, and they too are exhibiting the same slow behavior. I haven't ran filefrag on it yet, but something tells me the problem is there too. It seems like running it close to 100% usage for any amount of time is likely to start a cascading fragmentation effect. Perhaps there was a bug in a jfs implementation I used once, or a fsck.jfs run messed things up. 100,000+ is a bit absurd though and should never be reached in any real world conditions. On 1/28/07, Christian Kujau <li...@ne...> wrote: > On Sat, 20 Jan 2007, Jason Fisher wrote: > > I'm down to 75% usage now and write speeds in the root of that > > filesystem are still 5MB/sec. I do have a directory that gives me > > 180MB/sec writes -- I suppose it has a big set of contiguous blocks > > assigned to it. > > Interesting thread, really: I still wonder how other filesystems deal > with fragmentation over time. Sure, it's good to have >5% of free space, > this will be exceeded at peak times and the fs might be running at <1% > of free space until the bofh makes room again. but the fragmentation was > heavily increased during this "1% free period". > It's hard to reproduce too, because most fragmentation really > happens over time, methinks. > > For the record: I have a 30GB jfs on a single scsi disk, created > back in 04/2005 which acts as some kind of "scratch partition", so many > small files and at other times bigger dvd-images get written to the > disk. Often the partition has ~5% of free space, sometimes less. I just > dd'ed a DVD image from the partition to /dev/null...18MB/s it said... > > Christian. > -- > BOFH excuse #397: > > T-1's congested due to porn traffic to the news server. > |