I agree with Ian.
You'll pay extra for dedup storage whether it's an appliance or done via TSM.
TSM's will require extra resource (CPU, RAM) on the server, but will allow you
to use cheap, dumb storage. You'll pay a premium for disk storage associated
with an appliance, offsetting your savings from data reduction. IMHO, it's
probably a wash. We're going with TSM dedup, because we feel that TSM is in a
better location in the data flow, knows more about the data, and can do more
with it. I think one big reason that appliances are popular is that they were
available first.
When we compared cost of cheap dumb storage to dedup appliance, it was a wash,
unless you got high dd ratios. As we encrypt more data, those ratios become
more and more in doubt.
..Paul
On Nov 16, 2011, at 5:40 AM, "Ian Smith" <ian.smith AT OUCS.OX.AC DOT UK> wrote:
> Alper,
>
> We have tested TSM server-side deduplication and, yes, it works, but at a
> cost. Specifically, in our opinion the sum of
> the additional resource requirements (CPU power and memory) and the time
> required for the identification and reclamation processes meant that we
> couldn't see how server-side dedupe would scale on busy systems such as ours.
> Another factor that coloured our opinion was that not all our data deduped
> very well. As a result we are looking at client-side dedupe for those clients
> that we think will attain good dedupe ratios - however, client-side dedupe
> means longer client sessions and still impacts the TSM server a bit. I'm
> guessing that the apparent prevalence of hardware-based dedupe on this list
> is due to people realising that dedupe on a busy system needs to be offloaded
> from the TSM server.
>
> HTH
> Ian Smith
>
> On 16/11/11 06:32, Alper DİLEKTAŞLI wrote:
>> Hi Neil,
>>
>> We don't need LAN free backup and we won't that.
>> There is no problem about using file device class.
>> We won't change TSM license model.
>> We wonder about tsm deduplication is good and safe or not. We tested it in
>> the test system but we havent got experience on the production. If it can do
>> deduplication well(like as hardware solutions) we will buy an external disk
>> devices. If not we will buy a new LTO library and we won't use deduplication.
>>
>> Thanks
>> Alper
>>
>> -----Original Message-----
>> From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU] On Behalf
>> Of Neil Schofield
>> Sent: Tuesday, November 15, 2011 8:17 PM
>> To: ADSM-L AT VM.MARIST DOT EDU
>> Subject: Re: [ADSM-L] External Disk Unit and TSM Deduplication
>>
>> Alper
>>
>> I've been giving a bit of thought to this myself recently, although it's
>> more of an academic exercise since we're not in the market for a new library
>> at the moment.
>>
>> Some things you may want to consider:
>>
>> Do you (now or in the future) have a requirement for LAN-free backup? I
>> would expect this to be significantly harder with a FILE device class
>> compared to a physical/virtual tape library solution.
>>
>> Are you considering switching to a capacity-based TSM license model? If so
>> then I've been told that it's the volume of primary storage after TSM
>> de-dupe but before hardware-level de-dupe/compression that counts, which may
>> incline you more towards the disk-based solution.
>>
>> Either way I'd be interested to hear what you decide.
>>
>> Regards
>> Neil Schofield
>> Technical Leader
>> Data Centre Services Engineering Team
>> Yorkshire Water Services Ltd.
>>
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