Admittedly, flushing the small DSSU on the same spindles is more than 
twice as fast as the catalog.  As I have learned from this thread, NBU 
does not honor the tuned data buffer size when doing a catalog backup, 
but I'm skeptical it could make that huge of a difference.  64k vs 32k

Oh, and my example is NBU 5.1 MP6 on linux.


On Tue, 10 Jul 2007, Clooney, David wrote:

> One question would be is , how does the backup to tape work at
> acceptable speeds when using a NBU policy in the same environment ?
>
> Dave
>
> -----Original Message-----
> From: veritas-bu-bounces AT mailman.eng.auburn DOT edu
> [mailto:veritas-bu-bounces AT mailman.eng.auburn DOT edu] On Behalf Of Joe
> Royer
> Sent: 10 July 2007 15:49
> To: veritas-bu AT mailman.eng.auburn DOT edu
> Subject: Re: [Veritas-bu] Catalog performence to tape
>
> I have gone a few rounds with this issue myself, and here is what I
> learned:
> - Catalog disk needs read performance, not write.
> - RAID-5 is faster than RAID-10 for sequential reads.
> - If you put your catalog on SAN disk, don't use the same HBA/port that
> you use for tape.
> - Most servers' internal RAID controllers are brain dead
>
> My catalog is about 70GB and I can back it up from internal disk
> to LTO2 in about 50 minutes.  Given what I have seen in the past, I
> can't
> complain about this number.
>
> My master is an IBM x345 with six U320 SCSI drives.  Once upon a time
> (before me), it was configured with all six drives in a single RAID-5
> and
> when the catalog ran the OS would suffer because it was all the same
> virtual disk.  I had an opportunity to rebuild the box and I thought I'd
>
> be smart and change it up a bit.  I made a 2-disk mirror for OS, and a
> 4-disk RAID-10 for the NBU catalog.  This did not work well.  It turns
> out
> the internal LSI RAID controller is brain dead (as are most low-end raid
>
> controllers) and was doing a round robin read on what actually appeared
> to be a RAID-0+1.  So, my performance was actually worse than it was on
> a
> single spindle.
>
> As a temporary measure, I moved the catalog to SAN space.  It screamed.
> SAN was the best performance I have seen out of the catalog (see two
> HBAs
> above), but I wasn't too comfortable putting my catalog on SATA disk,
> SAN or not, so this was just a temporary home while I converted the
> 4-disk "RAID-10" to RAID-5.  Once this was complete, I had acceptible
> speeds again (above the minimum 10MB/s for my HP LTO2 drives).
>
>

-- 
Joe Royer / SysAdmin / Digital Motorworks / 512-692-1028


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