Slow Copy(CP) performance Post: 302359552

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Special Forums Hardware Filesystems, Disks and Memory Slow Copy(CP) performance Post 302359552 by zxmaus on Wednesday 7th of October 2009 12:56:18 AM

10-07-2009

Moderator

Since you don't tell us anything about your OS, your disklayout or anything else, we obviously have to guess, but in any case a copy from A to B that is slow is rather an IO issue than a cpu problem.
My best guess is, that both filesystems are maybe on the same disk and have maybe even different blocksizes. Since your filesystem was almost full, your fragmentation is very likely very high, since the OS had to put additional data where space were left, so typically the data was spread across the remaining diskspace and not nicely lined up like it would have been the case with lots of free space in the volumegroup. And I assume you haven't done a defragfs after cleaning up your diskspace.
When you now copy data from A to B and both locations are on the same disk, your system will take a lot more time to 1. find the data in the 'correct' order in filesystem A and read it - because its spread across the physical volume and 2. it will take a lot of time put the data back to disk in filesystem 'B' in the correct and suitable order - since the system has to find again free blocks big enough for your data chunks - and these chunks are likely as well spread across the entire disk.
Try to defrag your diskspace a few times, maybe that improves performance. If not, backup your data, drop the filesystems, defrag, recreate them and restore the content from backups.

Kind regards
zxmaus

zxmaus

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LEARN ABOUT BSD

quotacheck

QUOTACHECK(8)						      System Manager's Manual						     QUOTACHECK(8)

NAME

       quotacheck - filesystem quota consistency checker

SYNOPSIS

       quotacheck [ -v ] filesystem ...
       quotacheck [ -v ] -a

DESCRIPTION

       Quotacheck  examines each filesystem, builds a table of current disk usage, and compares this table against that recorded in the disk quota
       file for the filesystem.  If any inconsistencies are detected, both the quota file and the current system copy of the incorrect quotas  are
       updated (the latter only occurs if an active filesystem is checked).

       Available options:

       -a	      If  the  -a  flag  is  supplied  in  place  of  any filesystem names, quotacheck will check all the filesystems indicated in
		      /etc/fstab to be read-write with disk quotas.

       -v	      quotacheck reports discrepancies between the calculated and recorded disk quotas.

       Parallel passes are run on the filesystems required, using the pass numbers in /etc/fstab in an identical fashion to fsck(8).

       Normally quotacheck operates silently.

       Quotacheck expects each filesystem to be checked to have a quota files named quotas located at the root	of  the  associated  file  system.
       These defaults may be overridden in /etc/fstab.	If a file is not present, quotacheck will create it.

       Quotacheck is normally run at boot time from the /etc/rc.local file, see rc(8), before enabling disk quotas with quotaon(8).

       Quotacheck  accesses  the raw device in calculating the actual disk usage for each user.  Thus, the filesystems checked should be quiescent
       while quotacheck is running.

FILES

       quotas	      at the filesystem root

       /etc/fstab     default filesystems

BUGS

       The quotas file may be named arbitrarily but must reside in the filesystem for which it contains quota information.  Quotacheck	will  give
       the error:

	    %s dev (0x%x) mismatch %s (0x%x)

       if the quotas file is not in the filesystem being checked.  This restriction is enforced by the kernel but may be lifted in the future.

SEE ALSO

       quota(1), quotactl(2), fstab(5), edquota(8), fsck(8), quotaon(8), repquota(8)

HISTORY

       The quotacheck command appeared in 4.2BSD.

4.2 Berkeley Distribution					 January 24, 1996						     QUOTACHECK(8)