Milton,
Thanks VERY much for that info. That was exactly what I was looking for.
Also, "Please note that I originally posted this to Tab instead of the list
because I did not want it to seem that I was using the list to promote
Sepaton."
To the list: Milton is correct, but I wanted to query the forum with my
"why VTL" question.
Thanks again to all.
Tab
"Johnson, Milton" <[EMAIL PROTECTED]>
Sent by: "ADSM: Dist Stor Manager" <[EMAIL PROTECTED]>
06/16/2004 10:24 AM
Please respond to "ADSM: Dist Stor Manager"
To: [EMAIL PROTECTED]
cc:
Subject: Re: Tier'ed library
Tab,
We've asked the same thing and came to the following points:
1) The $/TB is about as cheap as you can get.
2) With a VTL you can do LAN free backups.
3) To create an equiv Primary StgPool using sequential-access FILE
volumes you would have to create a 200TB file system. Even using JFS2,
I'm not sure you would get the same throughput as with a VTL.
4) Sepaton claims that by second quarter 2005, they will also have
compression which would increase the VTL's "usable capacity". AIX does
not offer a compressed JFS2 filesystem, and if it did it would have to
have a serious impact on performance.
5) A tape library can be shared between systems which may/may not be
relevant to you.
6) We could not think of a "technical" advantage that favored using
sequential-access FILE volumes.
The biggest hurtle is changing your mind set to allow the use of disks
versus tape. We have come to the following conclusions:
1) If RAID-5 is that unreliable then why are we using it for our on-line
databases?
2) We will not be a "tape free" environment, we would just be replacing
our on-site tapes with disks. The amount of time when a backup is on
disks only is very short.
3) The VTL costs are low enough so that we can have a "mirrored on-site
tape pool". The mirror would be in another building and TSM would
simultaneously write the backup to both stgpools. This would give a
level of protection that would be very costly reproduce using physical
tapes.
The fact that IBM provides the service for the Sepaton VTL is an added
plus in our shop.
Please note that I originally posted this to Tab instead of the list
because I did not want it to seem that I was using the list to promote
Sepaton.
H. Milton Johnson
-----Original Message-----
From: ADSM: Dist Stor Manager [mailto:[EMAIL PROTECTED] On Behalf Of
Tab Trepagnier
Sent: Wednesday, June 16, 2004 8:48 AM
To: [EMAIL PROTECTED]
Subject: Re: Tier'ed library
Milton,
Thanks for the info. I briefly looked at Sepaton, but I had no idea
they were that inexpensive. I will probably give them a second look.
But one thing that I'm struggling with is "why a VTL?"
Between random-access DISK volumes and sequential-access FILE volumes
what does a VTL buy me that I couldn't implement using those two volume
types in TSM?
Thanks.
Tab Trepagnier
TSM Administrator
Laitram, L.L.C.
"Johnson, Milton" <[EMAIL PROTECTED]>
06/15/2004 03:13 PM
To: "Tab Trepagnier" <[EMAIL PROTECTED]>
cc:
Subject: Tier'ed library
Tab,
We are faced with the same options and are seriously looking at Virtual
Tape Libraries (VTL), an appliance that is physically a large SATA Raid
Array but presents itself to TSM as a tape library. The product we are
looking at is the Sepaton S2100-ES (www.sepaton.com). The things we
like include:
1) It's TSM certified, meaning that it has passed the same certification
the "real" tape libraries passed.
2) Cheap. We have been quoted $30K (USD) for the first 3TB and $18K
(USD) for each additional 3TB.
3) Modular: Purchase the first 3Tb then expand in 3TB increments up to
200TB. After that you purchase another VTL.
4) Performance: Since it's disk based it's very fast, up to 1.6 TB/hour.
Since the "tape drives" are virtual tape drives you can configure a tape
library to have 200 tape drives, eliminating the tape drive bottleneck.
"Tape mounts" happen instantly.
5) Because of the high performance and large number of available virtual
tape drives, you should be able to reclaim the virtual tapes when they
are only 25% reclaimable, instead of waiting until they are 50%
reclaimable. This should allow much more efficient usage of the "tape
space".
We will just use our present 3494 ATL to cut off-site tapes. We haven't
implemented it yet, but we are actively pursuing it.
Our contact is:
David Littman
The More Group
47 East Grove Street
Middleboro, MA 02346
[EMAIL PROTECTED]
508-946-2255 x19
H. Milton Johnson
