Hi, again, Toaster folks --
Thanks, Darren and Eyal, for taking the time to reply.
From your observations, it sounds like our choice for
"ultimate flexibility" with regard to volume sizing by
creating only one aggregate on our FAS960 was also a
choice away from fast backup speed for simultaneous dumps.
Is that a fair assessment?
Is anyone successfully running full simultaneous dumps to
separate tape drives (utilizing separate FC paths from the
filer to the fabric, and from the fabric to the drives) from
two or more aggregates on one filer (whatever model you may
have) at rated speed?
Eyal writes:
[...] adding shelves would actually help you achieve faster
dumps, not slower.
Would the shelves be best added to our existing two loops, or
would we do better to buy yet another HBA for them? Intuitively,
a busier loop doesn't sound like an optimal configuration; on
the other hand, we've been told that our FAS960's existing five
HBAs have pretty much maxed "all of the busses" in our FAS960.
While I'm trying to keep this discussion mostly about the system
architecture and what we should be able to expect for backup
performance, I can tell you that we're running DOT 7.0.4 while
waiting for a few more folks to run 7.2 for a while, and we are
getting ~80 MB/sec when dumping volumes individually. We dump
fulls once per month, and we can split up the monthly dump process
across a few nights if we absolutely have to. When we dump two
volumes simultaneously, the write speeds of the drives hover
around 40-50 MB/sec, and when we write three, they hover around
30-40 MB/sec.
Thanks again for your time & have a great day!
Don Glascock
--
Donald S. Glascock
Mailstop RO-SN-2-SPPDG
Special Purpose Processor Development Group
Mayo Foundation
4001 41st Street NW
Rochester, MN 55901
Glascock.Donald@Mayo.EDU +1.507.538.5467 +1.507.284.9171 (fax)
http://www.mayo.edu/sppdg/
"No matter where you go, there you are."
-----Original Message-----
From: owner-toasters@mathworks.com [mailto:owner-toasters@mathworks.com]
On Behalf Of Glascock, Donald
Sent: Tuesday, October 10, 2006 3:24 PM
To: toasters@mathworks.com
Subject: FAS960: backup speed vs simultaneous dumps...?
Hi, Toaster folks --
We're a small research group on our third Filer, which is
a single FAS960 with five shelves on two cross-connected 2-Gb
loops. We trigger flexVolume-level dumps of our one aggregate
directly to 2-Gb-fibre-connected LTO-3 drives.
When we dump two volumes simultaneously to two tape drives,
the time taken to dump each volume increases by a third to a
half again, compared to dumping each volume independently.
For example, a stand-alone dump may take two hours, but if
another dump of another volume to another drive is run
simultaneously, then that two-hour dump becomes a three-hour
dump. Adding a third simultaneous dump to a third drive causes
an even greater increase in dump times.
For diagnostic purposes, I've launched a conventional dump
of one volume triggered via NDMP our backup software, waited
for the dump to reach Phase-IV (the writing-data phase), and
launched from the FAS960's console a dump of another volume
to the FAS960's null device. Soon after this second dump
starts, the write speed on the tape drive associated with
the first dump falls off by quite a bit. This write speed
picks up instantly when I kill the second dump. Since the
second dump was only in Phase-I (inspecting files, but not
writing them), and since this second dump was to the local
null device anyway, I'm led to think that the performance
issues lie somewhere within the Filer's head and Disk I/O
subsystem.
With one-at-a-time backups of our volumes, our full backup
window is about eight hours (for about two terabytes). We
were planning to buy two more shelves in early 2007.
Should I expect a FAS960 to handle two or three simultaneous
full dumps without a significant loss in dump speed? Are you
getting nearly-linear performance out of your simultaneous dumps?
Thanks for your time & have a great day!
Don Glascock
--
Donald S. Glascock
Mailstop RO-SN-2-SPPDG
Special Purpose Processor Development Group
Mayo Foundation
4001 41st Street NW
Rochester, MN 55901
Glascock.Donald@Mayo.EDU +1.507.538.5467 +1.507.284.9171 (fax)
http://www.mayo.edu/sppdg/
"No matter where you go, there you are."
