generally speaking,
a disk subsystem represents a low granular data store.
Inspite of Raid and redundant power supplies,
you still have a single point of failure,
it can fail as a whole due to surge, firmeware or cabling error
or due to anything alse.
In this case you will loose all data.
Assuming you have primary storage pools on one ATA array
and Backup Pools on another ATA in another location,
you will loose (only) redundancy - but then all of it at once.
Comparing to it
a bunch of backup storage pool tapes saved in a safe
represent a higher-granular data store,
where you will normally loose only single tape(s) thus
only part of your redundancy.
... unless you consider a whole-safe disaster, which is
less probable comparing to whole-ata disaster,
but still possible.
On the other side, depending on technology used and care
it can be easier to loose (part of) data from one tape
comparing to loosing it from an raid-ed disk.
Is either of it it a problem or not?
Consult your business requirements.
regards
Juraj Salak
Austria
-----Ursprüngliche Nachricht-----
Von: Rainer Tammer [mailto:tsm AT SPG.SCHULERGROUP DOT COM]
Gesendet: Dienstag, 10. Juni 2003 17:08
An: ADSM-L AT VM.MARIST DOT EDU
Betreff: Re: anyone using ATA disk systems
Hello,
I see a very big problem in this disk storage pools.
If you have an surge on your electricity network you
can potentially loos all your data including the backup !!
Bye
Rainer Tammer
On Tue, 10 Jun 2003 10:43:35 -0400, John Underdown wrote:
>I also appreciate Mr. Railbeck feedback. We have been using an all disk
primary backup pool for over 4 years now and recently switch our copy pool
to all disk NAS located
at a remote site for DR. While Mr. Railbeck's comments may be correct in
theory, for me in practice they don't hold up. For instance he said "This
(no reclamation for random
access storage pools) can cause inefficient utilization of the disk space
over time" , my experience shows random access is still more efficient use
of space than sequential due
to the fact that I set my reclaim threshold for sequential media at 50%. For
me setting the reclaim threshold higher is not worth the additional
overhead.
>
>Also of note is Mr. Rialbeck's statement "We have not done a lot of testing
on this, so this can not be taken as a definitive statement". I suggest
anyone interested in an all
disk storage pool environment to test it for themselves.
>
>Considering TCO, that is, dirt cheap ATA's drives, lightening speed
restores, and an incredibility simple DR solution, an all disk storage pool
environment has been a real winner
with us. It's made me happy, the users happy, and most importantly
management happy.
>
>Thanks,
>
>john underdown
>SYNOVUS
>Phone:706-644-7592
>
>-----Original Message-----
>
>Date: Mon, 9 Jun 2003 17:04:07 -0400
>From: "Talafous, John G." <Talafous AT TIMKEN DOT COM>
>Subject: Re: anyone using ATA disk systems
>
>Mr. Raibeck,
> I appreciate your feedback and, being involved in IT for some 30 years, I
>understand the technical challenges involved. That is why I posted the
>question. With the falling cost of disk architecture, a disk to disk backup
>alternative seems to be coming close to rivaling disk to tape as a backup
>alternative. Especially when dealing with some of the more sophisticated
>tape solutions that involve the mainframe/zArchitecture.
> If I size my TSM solution such that I can recover 'x' number of
>application servers in a given number of hours, then I will require a
>certain number of tape drives based on the data transfer rate of each tape
>drive. Hence, any recovery process in DR mode is limited to the number of
>tape drives available. Ouch!!! With disk to disk, my limitation is the TSM
>server and the network.
> Add to the mix the fact that tape data transfer speeds are less than SCSI
>and/or ATA data transfer speeds and the thought is that with capacity of
>disk architectures increasing rapidly and the price currently lower than
>tape, it makes sense to back up everything to disk!!! Faster and lower
cost!
>So, I/we would appreciate IBM Tivoli's support of this concept.
> With all the pressure on budgets and all these jobs NAFTAing, I MUST
>arrive at the best solution! Thanks for your consideration.
>
>John G. Talafous IS Technical Principal
>The Timken Company Global Software Support
>P.O. Box 6927 Data Management
>1835 Dueber Ave. S.W. Phone: (330)-471-3390
>Canton, Ohio USA 44706-0927 Fax : (330)-471-4034
>talafous AT timken DOT com http://www.timken.com
>
>
>-----Original Message-----
>From: Andrew Raibeck [mailto:storman AT US.IBM DOT COM]
>Sent: Monday, June 09, 2003 1:33 PM
>To: ADSM-L AT VM.MARIST DOT EDU
>Subject: Re: anyone using ATA disk systems
>
>
>Addendum: I as I said earlier, we continue to study the matter. Possible
>outcomes include enhancements that will enable TSM to function better in
>an all disk storage pool environment, although we make no commitments at
>this time.
>
>Regards,
>
>Andy
>
>Andy Raibeck
>IBM Software Group
>Tivoli Storage Manager Client Development
>Internal Notes e-mail: Andrew Raibeck/Tucson/IBM@IBMUS
>Internet e-mail: storman AT us.ibm DOT com
>
>The only dumb question is the one that goes unasked.
>The command line is your friend.
>"Good enough" is the enemy of excellence.
>
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