Messages in this thread | | | Date | Wed, 23 Apr 2014 09:23:41 +0200 | From | Ivan Pantovic <> | Subject | Re: rm -f * on large files very slow on XFS + MD RAID 6 volume of 15x 4TB of HDDs (52TB) |
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> [root@drive-b ~]# xfs_db -r /dev/md0 > xfs_db> frag > actual 11157932, ideal 11015175, fragmentation factor 1.28% > xfs_db>
this is current level of fragmentation ... is it bad?
some say over 1% is candidate for defrag? ...
we can leave it like this and wait for a next full backup and then check on the fragmentation of that file.
On 04/23/2014 04:18 AM, Dave Chinner wrote: > [cc xfs@oss.sgi.com] > > On Mon, Apr 21, 2014 at 10:58:53PM +0200, Speedy Milan wrote: >> I want to report very slow deletion of 24 50GB files (in total 12 TB), >> all present in the same folder. > total = 1.2TB? > >> OS is CentOS 6.4, with upgraded kernel 3.13.1. >> >> The hardware is a Supermicro server with 15x 4TB WD Se drives in MD >> RAID 6, totalling 52TB of free space. >> >> XFS is formated directly on the RAID volume, without LVM layers. >> >> Deletion was done with rm -f * command, and it took upwards of 1 hour >> to delete the files. >> >> File system was filled completely prior to deletion. > Oh, that's bad. it's likely you fragmented the files into > millions of extents? > >> rm was mostly waiting (D state), probably for kworker threads, and > No, waiting for IO. > >> iostat was showing big HDD utilization numbers and very low throughput >> so it looked like a random HDD workload was in effect. > Yup, smells like file fragmentation. Non-fragmented 50GB files > should be removed in a few milliseconds. but if you've badly > fragmented the files, there could be 10 million extents in a 50GB > file. A few milliseconds per extent removal gives you.... > > Cheers, > > Dave.
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