Re: [Veritas-bu] NBU 6.5.6 client on FreeBSD 7.2 host

2010-09-10 15:54:56
Subject: Re: [Veritas-bu] NBU 6.5.6 client on FreeBSD 7.2 host
From: Bryan Bahnmiller <bbahnmiller AT dtcc DOT com>
To: Nate Sanders <sandersn AT dmotorworks DOT com>
Date: Fri, 10 Sep 2010 14:54:45 -0500


    Any filesystem you have will start out quickly but then drop in speed as it starts drilling down into the directory structure. The more directory levels you have, the slower it is. Which makes sense, since you are sort of following a tree structure down to the lower directory levels. Every time you drop down in a tree structure, you are branching to how ever many directories you have in that particular branch... And when you finish one branch, you pop back up a level and branch down to the next one. So you are following index links to index links to .... until you hit the actual file being backed up.

     Simple testing showed me long ago that the fewer levels you have in the directory tree, the quicker the backups. And depending on the filesystem, it can be orders of magnitude difference in speed.


Nate Sanders <sandersn AT dmotorworks DOT com>
Sent by: veritas-bu-bounces AT mailman.eng.auburn DOT edu

09/10/2010 02:02 PM

"veritas-bu AT mailman.eng.auburn DOT edu" <veritas-bu AT mailman.eng.auburn DOT edu>
Re: [Veritas-bu] NBU 6.5.6 client on FreeBSD 7.2 host

Okay so that multiplex test was user error. Didn't have "max streams per
drive" setup right. At 4 streams we saw 40MB/s, at 8 streams we see
50MB/s. But... we have a new problem. Within 1-2 minutes the I/O starts
dropping. At 3:00 minutes into an 8 stream job, we're down to 38MB/s.
Earlier when testing at 4 streams, we were 10 minutes in and I/O had
slowly dropped from 40MB/s down to 12MB/s.

What in the world is going on?

On 09/10/2010 01:41 PM, Nate Sanders wrote:
> Yes we are well aware of the limitations of NDMP and small files, thus
> the reason we're looking at trying NFS w/ snapshots. Our NetApp 6040 is
> peaking around 40-50MB/s but what the issue is right now is that we're
> getting such low performance from this FBSD box via NFS.
> I turned on multiplexing to 4, and we're still seeing only 3-4MB/s.
> On 09/10/2010 01:03 PM, Martin, Jonathan wrote:
>> I've tested NDMP on 6 differetnt arrays and it has never moved millions
>> of small files well. We maxed out backup performance on our NetApp FAS
>> 2xxx with 2 streams at approx 20MB/sec total.  We're hoping to test
>> SMTape, which purportedly does a bit level dump of the entire array.  I
>> haven't had a chance to test this yet, but according to NetApp it will
>> get us our weekly full and drive LTO3. We'll then need to put some sort
>> of forever incremental or snapshot backup in-between the SMTape dumps.
>> -Jonathan
>> -----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 Nate
>> Sanders
>> Sent: Friday, September 10, 2010 12:22 PM
>> To: veritas-bu AT mailman.eng.auburn DOT edu
>> Subject: [Veritas-bu] NBU 6.5.6 client on FreeBSD 7.2 host
>> Now that we made it to 6.5.6 we're able to start testing NFS performance
>> from our NetApp VS NDMP. For the longest time we've done the backup of
>> some 1 billion small image files off the NetApp via NDMP. This job
>> usually took 1-3 weeks to complete a full sweep via NDMP.
>> Since we have support for FBSD we thought we would try doing NFS via
>> that client as Linux NFS is not as powerful as the BSD/Solaris variety.
>> Well on our initial test of a small volume from the NetApp, we're seeing
>> 2-4MB/s performance. Confirmed via bptm log. This is going straight to
>> LTO4 tape, which usually backs up around 150MB/s. Logs show that the
>> previous NDMP jobs from the NetApp we're doing around 40MB/s direct to
>> two dedicated NDMP LTO4 drives.
>> Supposedly multiplexing for NDMP will come to NBU 7.x shortly and we
>> will test again with that in the future. Right now I am not multiplexing
>> this NFS job but while looking in bptm I don't see the usual "waited for
>> buffer" errors that would tell me that I _should_ increase it. Is it
>> still likely multiplexing would increase the overall performance here?
>> Is this a known issue with FBSD clients? Is there something else I
>> should be looking at?

Nate Sanders            Digital Motorworks
System Administrator      (512) 692 - 1038

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