Hmmm,
In that case, wouldn't the disks show 100% busy in nmon? AIX doesn't know about
the XIV back-end processing. And, we also see these pauses on other TSM servers
that are connected to an SVC.
No, I really think that something in TSM is slowing us down...
--
Gr., Remco
On 30 sep. 2010, at 11:20, Lloyd Dieter <ldieter AT ROCHESTER.RR DOT COM> wrote:
> I'm betting the pauses are the XIV destaging data from cache to physical disk.
>
> Not a big fan of using heavily cached disk LUNs for disk/file storage
> pools....
>
>
>
>
> On Wed, 29 Sep 2010 13:47:47 +0200
> Remco Post <r.post AT PLCS DOT NL> wrote:
>
>> Hi all,
>>
>> I'm currently testing TSM 5.5.4 on AIX 5.3 with an IBM XIV box.
>>
>> When I use dd or other tools to copy data off the disk to tape (LTO4), we
>> get quite a good performance, 100 MB/s or better. Even when backing up data
>> on the XIV via shared memory directly to tape, we're quite happy, we can
>> read the data at over 100 MB/s for one backup job, and for over 200 MB/s for
>> two jobs. But, when TSM uses the XIV for DISK volumes, we're not in a happy
>> place, backing up data from one XIV to TSM with diskpool on another XIV, we
>> get about 55 MB/s per backup job, best case. Both XIV boxes are otherwise
>> completely idle. When migrating data of the diskpool to tape, it's the same,
>> no matter what we do, we don't even get close to the LTO4 native
>> performance, about 70 MB/s is the best I've seen, and usually it's less. The
>> TSM server is at that time only running the migration, nothing else.
>>
>> The stragest thing we notice is that TSM seems to completely pause every so
>> often, no disk i/o, no tape i/o no cpu utilization, nothing for about one
>> second, and the it goes again. When I let two migration processes run, this
>> is less obvious, because one process continues while the other one pauses.
>>
>> We've opened a hardware call with IBM to find out if there are any settings
>> on the hdisks or HBAs that we need to change, and even though we did get
>> some hints, and some performance improvement out of that, we fell that TSM
>> should be able to do a lot better.
>>
>> Does anyone else have experience with XIV as a diskpool? and if so, what
>> sort of performance do you see?
>>
>> --
>> Met vriendelijke groeten,
>>
>> Remco Post, PLCS
>
>
> --
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