On Tue, 21 Jan 2014, Keith Keller wrote:
> On 2014-01-21, Steve Brooks <steveb@xxxxxxxxxxxxxxxx> wrote:
>>
>>> mkfs.xfs -d su=512k,sw=14 /dev/sda
>>
>> where "512k" is the Stripe-unit size of the single logical device built on
>> the raid controller. "14" is from the total number of drives minus two
>> (raid 6 redundancy).
>
> The usual advice on the XFS list is to use the defaults where possible.
> But you might want to ask there to see if they have any specific advice.
Thanks for the reply Keith. Yes I will ask on the list, I did read that
when built on mdadm raid devices it is geared up to tune itself but with
hardware raid it may take manual tuning.
>> I mounted the filesystem with the default options assuming they would be
>> sensible but I now believe I should have specified the "inode64" mount
>> option to avoid all the inodes will being stuck in the first TB.
>>
>> The filesystem however is at 87% and does not seem to have had any
>> issues/problems.
>>
>>> df -h | grep raid
>> /dev/sda 51T 45T 6.7T 87% /raidstor
> Wow, impressive! I know of a much smaller fs which got bit by this
> issue. What probably happened is, as a new fs, the entire first 1TB was
> able to be reserved for inodes.
Yes and the output of "df -i" shows only
Filesystem Inodes IUsed IFree IUse%
/dev/sda 2187329088 189621 2187139467 1%
So few inodes are used because the data is from "hpc" used to run MHD
(magneto hydro-dynamics) simulations on the Sun many of the files are
snapshots of the simulation at various instances "93G" in size etc.
>> Another question is could I now safely remount with the "inode64" option
>> or will this cause problems in the future? I read this below in the XFS
>> FAQ but wondered if it have been fixed (backported?) into el6.4?
>
> I have mounted a large XFS fs that previously didn't use inode64 with
> it, and it went fine. (I did not attempt to roll back.) You *must*
> umount and remount for this option to take effect. I do not know when
> the inode64 option made it to CentOS, but it is there now.
Ok so I am sort of wondering for this filesystem if it is actually worth
it given lack of inodes does not look like it will be an issue.
>> I also noted that "xfs_check" ran out of memory and so after some reading
>> noted that it is reccommended to use "xfs_repair -n -vv" instead as it
>> uses far less memory. One remark is so why is "xfs_check" there at all?
>
> The XFS team is working on deprecating it. But on a 51TB filesystem
> xfs_repair will still use a lot of memory. Using -P can help, but it'll
> still use quite a bit (depending on the extent of any damage and how many
> inodes, probably a bunch of other factors I don't know).
Yes this bothers me a bit, I issued a " xfs_repair -n -vv" and that told
me I only needed "6G" I guess with only a few inodes and a clean
filesystem it makes sense. I did read a good solution on the XFS mailing
list which seems really neat..
"Add an SSD of sufficient size/speed for swap duty to handle xfs_repair
requirements for filesystems with arbitrarily high inode counts. Create a
100GB swap partition and leave the remainder unallocated. The unallocated
space will automatically be used for GC and wear leveling, increasing the
life of all cells in the drive."
Steve
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