Networker

Re: [Networker] Advantages of disk to disk backup

2003-08-26 11:21:32
Subject: Re: [Networker] Advantages of disk to disk backup
From: Joel Fisher <jfisher AT WFUBMC DOT EDU>
To: NETWORKER AT LISTMAIL.TEMPLE DOT EDU
Date: Tue, 26 Aug 2003 11:19:29 -0400
Hey Mark,

I'm answering from personal research rather than experience...

Most hardware vendors claim that you will get better backup speed...
"Better" backup performance will be determined by how fast your current
tape drives are and how you configure the disk that your File Type
device resides on.  Since we have 60+ MB/s with compression drives, I
doubt very seriously we will see any substantial performance.  I
actually believe we will "lose" a little performance, but the gains IMHO
outweigh the losses IMHO.

The reasons we are heading towards D2D are below.
Much more reliable "media".  D2D will virtually eliminate media
errors(on the initial backup).

The "random access" abilities of the Advanced File Type Device.
(Although I think it is currently limited in legato.. only one stage or
clone while doing backups)

It should eliminate "tape" contention... ie when you're cloning a volume
that contains an saveset that someone is trying to restore.
Unfortunately due to some limitations of AFTD in legato you can't
restore and clone from the same device, so this is still a problem.
Possibly even a bigger problem because of the size(ie number of
savesets) of the AFTD will probably be larger than any single tape. At
least that is how it reads in the manual.  LEGATO PLEASE CHANGE THIS!!!

The major advantage is that recovery times of nearline savesets will be
almost immediate instead of having to wait for tape to be
loaded/mounted/fsf/fsr then read from.  And many users can recover
simultaneously with out contention.

Another advantage is that you can start cloning immediately after you
finish backing up because you tape drives will be dedicated for
cloning/staging rather than for backups then cloning/staging.

That's my 2 cents.

I'm doing an eval of several different ATA based arrays in the next
couple of months so I'll be able to give a better idea of performance
issues after that is complete.  I'll be checking out the Nexsan ATAboy2,
EMC Clariion CX600, StorageTek BladeStor, and NetApp NearStore.

Yes your data would still traverse the network.  Unfortunately you'll
have to weight the specific benefits/costs for your environment, but for
ours I believe the benefits are worth the cost.  AFAIK you can use a SAN
storage node to use SAN disk as a FTD, but then you can only backup
"local disk" to that FTD.

Please keep in mind that this is all based on what I read from the Admin
Guide and other docs not from experience, so I could possible be
interpreting sometime from the docs incorrectly.  Anyone feel free to
correct my misconceptions.

Have a good one,


Joel




Hi,  I am trying to determine the advantages of using disk to disk
backup for a Networker server.  The networker server would have 500gb of
disk and the total client data would be 200gb.  The client backups would
be performed across the network as the disk is attached to the networker
server. So my network will still be utilised by the backup, 

What kind of performance increase would I expect when using disk rather
than tape? (I realise that the model of server/disk will effect this so
in this case the disk will be internal to the compaq server).
Will the benefits be enough to recommend disk to disk backup rather than
a tape san?
Can I configure a SAN storage node to use SAN disk as a file type
device?


Thanks and Regards,  Mark


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