On Tue, 21 Jan 2014, Keith Keller wrote:
On 2014-01-21, Steve Brooks steveb@mcs.st-and.ac.uk 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