Re: 2TB USB hard drive for backing up: XFS info
On Fri, 04 May 2012 15:08:57 -0400, Chris Knadle wrote:
> On Monday, April 30, 2012 10:53:46, Camaleón wrote:
>> On Sun, 29 Apr 2012 20:16:58 +0200, Martin Steigerwald wrote:
>> > Am Dienstag, 24. April 2012 schrieb Camaleón:
> ...
>> > XFS might also have long file check times.
>>
>> I still have not tried this so I can't really tell but what I've heard
>> on XFS is not comparable to ext3, I mean, in regards with the time it
>> takes to perform a filesystem check.
>
> On XFS, fsck is literally a no-op -- it does *not* fsck the filesystem.
Well, at least there are "xfsprogs".
> The steps to actually fsck a XFS filesystem:
> - mount the XFS filesystem to replay the log
> - unmount the XFS filesystem that was just mounted
> - run xfs_check on the filesystem's device
> - if necessary run xfs_repair on the filesystem's device
You mean you don't even notice a file system inconsistency until it
royally crashes or even something worse? Oh.
> Note this means running 'xfs_check' is done when the filesystem is not
> mounted. _Supposedly_ it can also be run if the filesystem is mounted
> read- only, but in practice I find it's best (and easier) to run the XFS
> commands from a LiveCD. The xfs_check and xfs_repair operations are
> incredibly fast -- even for a 500GB filesystem it's usually only takes
> about 10 or 15 seconds. Speed is generally what XFS is good at, *except*
> when it comes to deletion of a large number of files -- that's where
> it's slow.
So... is that you don't find it suitable for a standard "/" partition?
I mean, if it's better don't analyze an XFS partition when is mounted
read-only, that can be really a no-no for many installations running
24/365.
> Also in practice I find that any kernel crash or hard-power-off corrupts
> XFS to at least some extent requiring an xfs_check and xfs_repair, so I
> have to make sure to keep a LiveCD on hand to be able to do this.
I've also heard about terrific stories of data lose after an unexpected
power failure on volumes running on XFS but as I said before, I have no
direct experience with this file system so I can't comment.
> This gets even more interesting when running XFS on top of LUKS
> encryption. I'm currently doing that, and I have had to do an xfs_repair
> operation -- it involves running cryptsetup manually at the command line
> within a LiveCD and then running xfs_repair on the newly created
> unencrypted device. [And of course you have to know to look and make
> sure the LiveCD contains those utilities.] Definitely an interesting
> experience.
File systems need a twist :-)
> The main reason I've been running XFS is for speed -- even on top of
> LUKS I'm finding XFS is able to do sustained 40MB/s transfers over 1Gb
> ethernet, where ext4 on the same box is not able to sustain that.
> However ext4 is more reliable and easier to deal with, because it's able
> to run an fsck at boot time and without neeting a LiveCD to fix it. ;-)
Not bad numbers.
In the event I give XFS a whirl it will be over my "/data" partition,
that's for sure... and fortunately all of my system have UPS units on
behind O:-)
Greetings,
--
Camaleón
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