On October 13, 2015, Daniel Fussell wrote: > ext4 has a defragger, but I've never used it. Occasionally I will get
> curious and run filefrag to find out how many extents each file has. I Okay. Now my lack of experience in the last ten years is coming back to haunt me. Perhaps this is a simple question, and if so I'm sorry, but I have to ask. What the heck is an extent? Realize I've never even seen ext4. I was just getting used to a journaling ext2 (aka ext3) when I was forced to stop using Linux for some time. I'm only now getting back into things. Frankly, I don't care if I use Ext4, XFS, Btrfs, or something else on this file system I'll be setting up. But I do expect some heavy fragmentation due to multiple downloaders functioning at once (I would not be surprised to see six or seven files being written to at once). My only requirements are that it be a fast filesystem, and that there be some way to reduce the fragmentation to a minimum so that for later transfers the read speed is as close to the max combined speed for the multiple HDDs in the volume as possible. And If I was to use XFS or Btrfs, I'd probably want to look into Data Deduplication as well, but that's not a guarantee. I've certainly heard of XFS before, and it sounds like it might suit the bill quite nicely. But if I do use it, how do I setup these "extents" you speak of? And what is a good size for the extent? This volume will store some programs, but mostly multi-media files (approx 10% programs, 90% multi-media, of which 95% will be video files). Thanks for any ideas here! --- Dan On Tue, Oct 13, 2015 at 1:26 PM, Daniel Fussell <[email protected]> wrote: > On 10/13/2015 02:44 AM, Dan Egli wrote: > > I was wondering if anyone had heard of any utilities that would allow one > > to defragment a Linux Native file system (i.e., ext4, btrfs, etc...)? > > Considering how much mechanical HDD performance falls due to > fragmentation > > I'd think there would be at least one, but I can't think of it. Can > anyone > > else? > > > > > > > > Thanks! > > --- Dan > > > > > ext4 has a defragger, but I've never used it. Occasionally I will get > curious and run filefrag to find out how many extents each file has. I > just ran e4defrag -c on my root and home volumes, and it found very > little fragmentation in my home, and only mild fragmentation in my > root. I might defrag my root for fun, but I doubt I'll see any > improvement. > > xfs has xfs_fsr, and I've used it a few times. But xfs_fsr defrags > different than you would expect. It only reorganizes the most > fragmented files one pass at a time, and stops after a specified time > limit. The downside is, if the aggregation group doesn't have enough > contiguous space to store the defrag-ed file, it will look in other > aggregation groups for space. Normally, all files in a directory are > created within the same aggregation group to improve locality. So > depending on your workload, defragging may hurt performance more than it > helps. > > The only time I've defragged XFS where it helped was when I ran a MythTV > box with two capture cards. Then I got smart and set XFS for minimum of > 64MB extents in my video storage pools. That did more for preventing > fragmentation and helping performance than defragging ever did. > > Defragging other filesystems can be done by tarring up the volume to a > separate device, deleting all the (regular) files, and untarring back in > place. It isn't fast and can't be done online, but you certainly have > the option. > > Grazie, > ;-Daniel > > > > > /* > PLUG: http://plug.org, #utah on irc.freenode.net > Unsubscribe: http://plug.org/mailman/options/plug > Don't fear the penguin. > */ > /* PLUG: http://plug.org, #utah on irc.freenode.net Unsubscribe: http://plug.org/mailman/options/plug Don't fear the penguin. */
