Re: [Veritas-bu] T2000 vaulting performance with VTL/LTO3

Not sure if this question was directed at Mike or myself, but if it was
directed to me...

In our case, the memory buffers for the disk are the shared memory
buffers on the media server (T2000).  When a media server is backing up
itself, the bpbkar process reads from disk directly into the
shared-memory buffers - the same buffers that the bptm process is
writing to tape from.  So, for our filesystem backups, we see disk I/O's
of the same size as our tape buffers...  We're currently bottlenecked at
the front-end processors of our storage array, and doing fewer larger
I/O's provides a little more throughput from the array.

The cache on the storage array is something I don't have a whole lot of
understanding about.  I assume that for reads, it is mostly a buffer
space for readahead...

-devon

-----Original Message-----
From: Justin Piszcz [mailto:jpiszcz AT lucidpixels DOT com] 
Sent: Wednesday, November 21, 2007 6:59 AM
To: Mike Andres
Cc: Peters, Devon C; VERITAS-BU AT mailman.eng.auburn DOT edu
Subject: Re: [Veritas-bu] T2000 vaulting performance with VTL/LTO3

Buffers in memory to disk would be dependent on how much cache the raid 
controller has yeah?

Justin.

On Wed, 21 Nov 2007, Mike Andres wrote:

> I'm curious about NUMBER_DATA_BUFFERS_RESTORE and duplication
performance as well.  Anybody know this definitively?
>
> ________________________________
>
> From: veritas-bu-bounces AT mailman.eng.auburn DOT edu on behalf of Peters,
Devon C
> Sent: Tue 11/20/2007 1:32 PM
> To: VERITAS-BU AT mailman.eng.auburn DOT edu
> Subject: Re: [Veritas-bu] T2000 vaulting performance with VTL/LTO3
>
>
>
> Chris,
>
> To me it looks like there's a 1Gb bottleneck somewhere (90MB/s is
about all we ever got out of 1Gb fibre back in the day).  Are there any
ISL's between your tape drive, your switch, and your server's HBA?
Also, have you verified that your tape drives have negotiated onto the
fabric as 2Gb and not 1Gb?
>
> When we had 2Gb LTO-3 drives on our T2000's, throughput to a single
drive toped out around 160MB/s.  When we upgraded the drives to 4Gb
LTO-3, throughput to a single drive went up to 260MB/s.  Our data is
very compressible, and these numbers are what I assume to be the
limitation of the IBM tape drives.
>
> Regarding buffer settings, my experience may not apply directly since
we're doing disk (filesystems on fast storge) to tape backups, rather
than VTL to tape.  With our setup we see the best performance with a
buffer size of 1048576 and 512 buffers.  For us these buffer sizes are
mostly related to the filesystem performance, since we get better disk
throughput with 1MB I/O's than with smaller ones...
>
> I'm also curious if anyone knows whether the
NUMBER_DATA_BUFFERS_RESTORE parameter is used when doing duplications?
I would assume it is, but I don't know for sure.  If it is, then the
bptm process reading from the VTL would be using the default 16 (?)
buffers, and you might see better performance by using a larger number.
>
>
> -devon
>
>
> -------------------------------------
> Date: Fri, 16 Nov 2007 10:00:18 -0800
> From: Chris_Millet <netbackup-forum AT backupcentral DOT com>
> Subject: [Veritas-bu]  T2000 vaulting performance with VTL/LTO3
> To: VERITAS-BU AT mailman.eng.auburn DOT edu
> Message-ID: <1195236018.m2f.181149 AT www.backupcentral DOT com>
>
>
> I'm starting to experiment with the use of T2000 for media servers.
The backup server is a T2000 8 core, 18GB system.  There is a Qlogic
QLE2462 PCI-E dual port 4Gb adapter in the system that plugs into a
Qlogic 5602 switch.  From there, one port is zoned to a EMC CDL 4400
(VTL) and a few HP LTO3 tape drives.  The connectivity is 4Gb from host
to switch, and from switch to the VTL.  The tape drive is 2Gb.
>
> So when using Netbackup Vault to copy a backup done to the VTL to a
real tape drive, the backup performance tops out at about 90MB/sec.  If
I spin up two jobs to two tape drives, they both go about 45MB/sec.   It
seems I've hit a 90MB/sec bottleneck somehow.  I have v240s performing
better!
>
> Write performance to the VTL from incoming client backups over the WAN
exceeds the vault performance.
>
> My next step is to zone the tape drives on one of the HBA ports, and
the VTL zoned on the other port.
>
> I'm using:
> SIZE_DATA_BUFFERS = 262144
> NUMBER_DATA_BUFFERS = 64
>
> Any other suggestions?
>
>

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