You are right about the 9840's; they are just screaming fast; I like them
even better than 3590's for TSM for that reason. Also incredibly robust.
We had some 9840's that we ran days on end, 20 hours a day, doing enormous
amounts of reclaims (read LOTS of start/stop activity), with no drive or I/O
errors.
We had to give them up because, as you said, the cartridges are only 20 GB
native, and we outgrew our (non-expandable) 9710 robot before the 9840C
became available.
I've never used the 9940's, but if you dig around the web site, STK clearly
says that the 9840's are performance and the 9940's are for capacity.
I asked our CE at the time, and he said there is no real difference in the
9940 drive mechanics, it should be as reliable as the 9840.
BUT, the big difference is that the 9840 is a 2-reel cartridge that loads
from the middle; and that is one big reason it is so spritely. The 9940 is
a single-reel cartridge, loads from the end. So I don't believe it is
physically possible to maintain the same performance on small file restores.
That being said, the only cartridges I am aware of that have the middle load
point are the 9840 and the old Magster 3570 (no longer marketed). The LTO
standard called for a fast, 2 reel LTO Accelis cartridge to be built for
speed as well as the Utrium cartridge that was built for capacity; but the
last time I checked the LTO web site it said that the LTO Ultrium as worked
so well that no vendor is ever going to build an Accelis drive.
And I don't know that the 9940 wouldn't still give you adequate performance,
just offering some points for you to consider.
I would call and ask your local STK office to provide you with some stats
for the 9940 vs. the 9840C, I'm sure they'll be HAPPY to comply.
Wanda Prather
"I/O, I/O, It's all about I/O" -(me)
-----Original Message-----
From: John Benik [mailto:John_Benik AT BLUECROSSMN DOT COM]
Sent: Friday, March 26, 2004 9:33 AM
To: ADSM-L AT VM.MARIST DOT EDU
Subject: Re: 9840 vs 9940 Performance
I'd be interested in seeing this also, we are looking at 9940's as well.
You may want to look at the 9840C cartridges which have a lot more
capacity, and will allow you to keep the same drives...
John Benik
Blue Cross Blue Shield of Minnesota
Storage Administration and Performance
W. (651)-662-4955
P. (651)-610-5080
"Frost, Dave" <Dave.Frost AT SUNGARD DOT COM>
Sent by: "ADSM: Dist Stor Manager" <ADSM-L AT VM.MARIST DOT EDU>
03/26/2004 04:23 AM
Please respond to
"ADSM: Dist Stor Manager" <ADSM-L AT VM.MARIST DOT EDU>
To
ADSM-L AT VM.MARIST DOT EDU
cc
Subject
9840 vs 9940 Performance
Hello all,
Does anybody have any experience with TSM performance of STK 9940's ?
We are running 9840's with colocation and have found the performance for
large restores of a small file nature to be very good.
The only problem with 9840 is the 20GB limitation. I know that large
servers will span multiple tapes and the multi-thread restore works
exceptionally well with this. The only problem is that with growing data
quantities, an L700 fills up very quickly.
Using 9940's would triple the capacity of an L700. But we need to ensure
we
would maintain the performance that we are seeing on the 9840's.
I understand that a 9940 is going to be a physically longer tape and as
such certain stats are not comparable to the 9840. But does the
repositioning and backhitching that is so evident with a large TSM restore
compare to that of a 9840.
-=Leigh=-
|
