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Re: File read speed *strongly* degraded on one partition only

On Tue, 27 May 2003 08:26, Chris Metzler wrote:
> Hi.  I am really befuddled with this one.  I've checked the archives
> of this list for anyone reporting anything similar, I've googled, and
> haven't found anything useful.
> Yesterday, I abruptly started suffering from extremely slow disk reads
> from my /home partition.  The symptoms are truly odd:  not only have the
> parameters of the drive (checked through hdparm) not changed -- still
> using dma etc. -- but the problem isn't present on all the partitions
> of that drive.  If I copy a large file from /home to a different partition
> on the *same drive* (which takes forever, because the read of the original
> on /home is very slow), and then read from the new copy of the file on the
> other partition, it reads about 15-16 times more quickly.  The drive is not
> slow; only that partition is.
> Can anyone point me at anything that would help me figure out what's going
> on, and how to recover my lost I/O speed?  What am I missing here as to why
> this would occur?
> Filesystem           1K-blocks      Used Available Use% Mounted on
> /dev/hde10            56563100  49769796   6793304  88% /home

Wild guess - the 88% full may be your problem.

> So everything looks normal, the same on all the drives, until the file
> manipulation starts.  A 651 MB file is copied from its location on /home
> to the first 120 GB drive, /mnt/b1; the two files are then compared to
> each other.  Using "time", the copy takes 250s while the compare takes
> 255s -- more than 4 minutes.

I have found that comparing large files is done quicker by doing an md5sum on 
each instead of diff. In my case the files are always on the saem ide chain 
so YMMV.



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