Re: Performance with move data and LTO3

Nice one! I get back on this after the Holidays.

Thanks
Henrik 

-----Original Message-----
From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU] On Behalf Of
Prather, Wanda
Sent: den 19 december 2006 18:15
To: ADSM-L AT VM.MARIST DOT EDU
Subject: Re: Performance with move data and LTO3

Interesting.

Differences in IBM vs. HP LTO3 drives:

   I have been told that the IBM drives do "smart" compression using a
bypass buffer.  If a block of data is going to expand during
compression, the IBM drives will stop compression and write the
uncompressed block, which should make them a bit faster.

Re tape to tape operations:

   I have observed the same behavior; tape to tape operations are
inexplicably slower than you would expect when the TSM server is on
WINDOWS.  I have observed this with fibre drives, and SCSI drives, 3590
and LTO.  I suspect it has something to do with buffer use, but since
Windows provides no tools whatever to measure performance of tape
devices or buses with tapes on them, I've never been able to make any
other determination.  

I don't think it is a READ issue with the drives.  Try testing using an
AUDIT; that just reads the tape and doesn't write anything.  I suspect
you'll get faster READ times.  I would be interested in seeing your
results!



Wanda Prather
"I/O, I/O, It's all about I/O"  -(me)


 

-----Original Message-----
From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU] On Behalf Of
Henrik Wahlstedt
Sent: Thursday, December 14, 2006 10:37 AM
To: ADSM-L AT VM.MARIST DOT EDU
Subject: Performance with move data and LTO3

Hi,

I wonder what transfer rates (move data from drive to drive) I am
supposed to see with LTO3.

I have two TSM servers, one 32-bit Win2k3 and one 64-bit 2.6.9-11.Elsmp,
with a SL500 and FC LTO3 drives. 
Similar HW (HP DL585) except for one server have HP- and the other have
IBM drives. Drives are on separate PCI busses.

I used a dataset of 50Gb with large files, same file type on both
systems. Only scratch tapes and no expiration on the datasets.
No other tape activity on the systems during the tests.

I tested disk->mt0->mt1->mt2->mt3->mt1->mt0->disk
>From disk to tape I get a throughput of 74-76Mb/s with IBM drives,
(migration).
>From tape to tape, (move data), with HP drives I get a throughput of
30-46Mb/s and with IBM drives I get 39-59Mb/s.
>From disk to tape, (move data), with IBM drives I get a throughput of
44Mb/s.

Apperently write speed seems OK but read spead is an issue?! Or is this
normal?



Thanks
Henrik




















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