Re: Server-Free Backup is it for real or is it just a Hype

I vote for hype.

If we look at TSM definition of "server-free" backup (SAN Xcopy moving 
disk to tape implemented by SAN switch/router) even if is not a hype but 
for me is very close. The technology behind 3rd party copy is very 
simplified, dumb and hard to coordinate with any other application/system 
in the enterprise.

If we broaden the definition to include other smarter devices which are 
neither the application nor backup server, server-free is quite real and 
used in production long since. Examples:
- backup from another server of mirrors made using EMC's BCV, HDS's 
ShadowImage or IBM's FlashCopy;
- remote disk storage copies made using EMC's Symmetrix Remote Data 
Facility, HDS's Hitachi Extended Remote Copy or IBM's Peer-to-Peer Remote 
Copy/eXtended Remote Copy;

The difference here is how smart is the device used to move the data. The 
SAN switches/routers are devices made for specific purpose, dumb enough, 
and tuned for performance of main functionality. Implementation of 3rd 
party copy is very generic and thus difficult to use and ineffective.
Next level of smartness are disk storage servers. They have sophisticated 
controllers inside, with lot of memory and enough processing power to 
perform more types of copy operations. OTOH those servers do not mess with 
filesystem structure inside LUNs. Even if they try it would be nearly 
impossible to synchronize the efforts with application server's operating 
system and filesystem's cache.
So we need even smarter device, capable to understand the specific 
filesystem's internal structure, read the files, send the data to a disk 
or tape. Usually such device is called a server :-) This is a task for 
well-known LAN-free TSM Storage Agent.

So what is Server-Free and where is it positioned? My opinion is 
server-free is oversimplified edition of LAN-free. If it has to become 
functionally equivalent to storage agent then it would become equally 
complex.
I remember reading somewhere an argument against simplification of 
taxation laws - that complexity was introduced to satisfy many 
requirements and plain simple rules will have to be ammended several times 
to meet those requirements thus the result on the end will be of same 
complexity.

Zlatko Krastev
IT Consultant






Pétur Eyþórsson <peddi AT ITN DOT IS>
Sent by: "ADSM: Dist Stor Manager" <ADSM-L AT VM.MARIST DOT EDU>
04.04.2003 16:25
Please respond to "ADSM: Dist Stor Manager"

 
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        Subject:        Server-Free Backup is it for real or is it just a Hype


Hi Guys.

I want to start a discussion on Server-Free Backup.

Server-Free backup is to bee the holy grail in SAN backup. Server free
backup is just when you tell something on the san backup these files, and 
it
will copy disk to disk or disk to tape or what ever you want. This will 
make
use of the SCSI 3´rd party command (XCOPY), and it´s real easy to write 
code
that can recive that command and do the read and write because all the 
work
is done, because it all comes down to "i want this track and block copyed 
to
this device". Whats hard to do is to build that command in the fist place.
File space has to bee written such that they will accept a request for a
3´rd party copy command and they haft to have a API so that the 
applications
know that it´s possible or the application has to go around the file 
system
and write directly to the SCSI adapter and then it got to figure out where
all those files are. So the kind of Server Free Backup going on today is
realy full volume backup where it´s jst block 0, block 1, blcok 2 and its
more of a Server Free dump than a Server Free Backup.

So my point is that when you use software to do a block level backup on 
the
SAN. I belive that hardware, where you have firmware microcode will always
be better than software. kinda like hardware raid vs software raid.

I dont see any true benefits from using Server Free backup because today
you´ll alwayes bee bound to full volume backup, and there are usualy mutch
beter deviceses out on the san that can do that. The only scenario i see
where Server Free backup would be acceptable is when you can start doing a
file level backup. but that just isn´t possible today.

I belive Server Free backup is just a sales hype, Server Free isn´t ready
and wont be for many years to come.


Please share your thoughts on my statement.
Kvedja/Regards
Petur Eythorsson
Taeknimadur/Technician
IBM Certified Specialist - AIX
Tivoli Storage Manager Certified Professional
Microsoft Certified System Engineer

peddi AT itn DOT is

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