2) Sepaton does hardware compression so as far as I can tell it performs like
compression on physical drives, I imagine other vendors may also use hardware
compression. Besides what's important to me is that my TSM clients and TSM
server are not taking a performance hit from doing compression because
compression has been off loaded to the VTL. Even if the VTL performs slower
when compressing vs not compressing, it's not an issue unless your TSM server
can over whelm your VTL. Any time your TSM server or TSM client is doing
compression, your backup session performance is impacted.
3) This is an area that merits actual testing which is one reason I expressed
it as a personal opinion. This seems to me that the results would be very
dependent upon the exact hardware configuration being tested. At the least,
using a VTL would off-load the file system management activities from the TSM
server to the VTL freeing up TSM CPU cycles to pump data from the input stream
to the output stream.
4) Read the article by Curtis Preston (referenced in the "Just how does a VTL
work?" thread) for a discussion on in-band versus out-of band de-dup and the
effect on performance. I agree this technology does not have a long track
record and due diligence in progressing on this, and other new backup
technologies, is strongly advised. As I stated I have not used this as of
"yet".
5) If your VTL must run FSCK against 100TB, yes you do have a problem but:
5A) At least your TSM server is up.
5B) Your TSM server is a much more complex system compared to a VTL. Hence is
most likely more susceptible to crashing.
Thanks,
H. Milton Johnson
-----Original Message-----
From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU] On Behalf Of
Josef Weingand
Sent: Sunday, June 17, 2007 2:58 PM
To: ADSM-L AT VM.MARIST DOT EDU
Subject: Re: [ADSM-L] Fw: How to Incorporate a CDL into TSM environment?
1.) yes
2.) pls give me vendor / machine type of VTLs which does compression without
performance impacts.
physical tape drives gets performance improvements of compression, but VTL gets
normally much slower performance if compression is enabled
3.) you need compare the same technology. You need compare a FC Disk
Subsystems, like DS4000, with a VTL, then you get the same performance (maybe
even more) from a File Device Type as from a VTL.
4.)current de-dups does not bring enough performance for most of the
environments, and in addition, most vendors have just announced it, but does
not have it ready for GA yet.
5.)what happens if the VTL crashed????
Mit freundlichen Grüßen / Kind regards
Josef Weingand
Senior IT Specialist
Technical Sales Systems Storage
Mobil +49 171 55 26 783 - Homeoffice Tel. +49 8845 757421 Fax +49 171 13 5526783
email: weingand AT de.ibm DOT com
SMS/eMail: 01715526783 AT t-d1-sms DOT de
IBM Deutschland GmbH
Vorsitzender des Aufsichtsrats: Hans Ulrich Maerki
Geschäftsführung: Martin Jetter (Vorsitzender), Rudolf Bauer, Christian
Diedrich, Christoph Grandpierre, Matthias Hartmann, Thomas Fell, Michael Diemer
Sitz der Gesellschaft: Stuttgart
Registergericht: Amtsgericht Stuttgart, HRB 14562 WEEE-Reg.-Nr. DE 99369940
"Johnson, Milton" <milton.johnson AT CITI DOT COM> Sent by: "ADSM: Dist Stor
Manager" <ADSM-L AT VM.MARIST DOT EDU>
15.06.2007 21:08
Please respond to
"ADSM: Dist Stor Manager" <ADSM-L AT VM.MARIST DOT EDU>
To
ADSM-L AT VM.MARIST DOT EDU
cc
Subject
Re: [ADSM-L] Fw: How to Incorporate a CDL into TSM environment?
Why a VTL vs FILE devclass volumes on local drives?
1) With a VTL you can do LAN free backups.
2) Data Compression:
2A) TSM Client does compression: Big performance hit on the client,
slower backups/restores
2B) TSM server does compression (FILE devclass volumes on compressed
file systems): Big performance hit on server, slower
backups/reclaims/restores
2C) VTL does compression: No performance hits (just as with using
physical drives with compression)
3) I doubt the TSM server could write large amounts of data
simultaneously streaming in from 30 different clients to 30 different
FILE devclasses volumes as fast as it can write that data to a fibre
channel adapter.
3A) 30 input streams means 30 mounted FILE devclass volumes
3B) The drive heads would always be out of position for the next write.
4) Data Reduction/Data Deduplication/Content Aware Compression: What
ever the VTL vendor calls it, you don't have that available with FILE
devclass volumes. (I realize that from previous posts you are not
comfortable with this technology, I myself have not used it.)
5) Do you really want to manage an AIX system with a 25TB, 50TB or a
100TB file system? After a system crash how long will a FSCK of 100Tb
take?
Thanks,
H. Milton Johnson
-----Original Message-----
From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU] On Behalf Of
Allen S. Rout
Sent: Thursday, June 14, 2007 3:22 PM
To: ADSM-L AT VM.MARIST DOT EDU
Subject: Re: [ADSM-L] Fw: How to Incorporate a CDL into TSM environment?
>> On Wed, 13 Jun 2007 08:43:43 -0400, "Johnson, Milton"
<milton.johnson AT CITI DOT COM> said:
> The VTL is a Sepaton S2100-ES and yes it is disk only.
> I don't see the benefit that a "tape backed" system would bring, how
> does that really differ from a physical tape ATL with TSM providing a
> DISKPOOL front end?
Well, exactly. :)
But the distinction I wanted to make clear was: if you've decided to
store all your data on disk, then TSM has all the primitives necessary
to make that disk manageable, and you can discard the intermediate
appliance that makes the disk pretend to be a bunch of tape drives.
That's what everyone's getting at when they talk about FILE devclasses.
So if you bought 23 TB of slow disk plus a pretend-im-tape-box, then the
tape box was a waste, if you're using TSM. If you're using something
without TSM's volume primitives, it could be extremely important.
- Allen S. Rout
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