Re: [BackupPC-users] [Solved] Slow web-GUI access

>-----Original Message-----
>From: Les Mikesell [mailto:lesmikesell AT gmail DOT com]
>Sent: Tuesday, May 11, 2010 5:07 PM
>To: backuppc-users AT lists.sourceforge DOT net
>Subject: Re: [BackupPC-users] [Solved] Slow web-GUI access
>
>Read access is normally OK on a raid5.  The issues are that with a small
>number of drives you essentially force all the heads to seek together to
>handle writing the parity and on partial block writes you have to read
>first, then rewrite to update the parity.  So you slow down to the seek
>time of the slowest drive.  If you noticed speed issues even when
>backups were not writing to the array you probably had some other
>problem.  Did you check (cat /proc/mdstat) to make sure all the drives
>were working?  Perhaps it was running degraded and your eventual failure
>was when a 2nd drive dropped out.

So was my understanding too; that raid5 read performance was ok.

What is a small number of drives? I have three identical 500GB Seagates of the 
SATA2 variety, all bought new late last year, so I'm assuming fairly modern as 
well.

My checks in /proc/mdstat showed nothing unusual. They've been working fine 
all the time, all three of them; ie none is failed.

The backup of the linux machines here, is for the most part hundreds of 
thousands of really small files, like in the 10-100kB-range. Could this be a 
reason for slowness? I'm thinking that with so many small files, the write 
portion of the backup can't really "take-off" as it would with a really big 
files. Or maybe it doesn't really matter. This whole thing with what 
filesystem to use etc depends a lot on what you're planning to backup. I have 
most of everything, really small files all mixed up with really enormous ones.
-- 
/Sorin

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