Boot from SAN - Why not?
 

Malcolm Weir wrote in
:
If you're going to pick nits, I may as well add that 2Gb is actually
something like 212.5MiB/sec (it's a serial protocol, so the raw bit
rate has to carry an encoding of the data, just as a async 9600 baud
line could only carry 960 bytes/sec, each consisting of 1 start, 1
stop, and 8 data bits). And then there's a framing overhead, too...

It's actually 200 MB/sec (not MiB) due to the fact that every byte is
encoded as 10 bits and signaling rates are measured in SI units.


--
/Jesper Monsted

The main reason I recommend having the swap and boot disks on SAN and
not DAS is for availability. If the internal disk fails, the system is
down and therefore whatever app is running on it. Even if you have
mirrors in the internal disk many systems require shutdown to replace
those disk, especially when it is scsi. The OS is just as valuable as
your application... Without it, your app is dead anyway..
THop

netwuffus wrote:

Christian Reiter wrote in message . ..

Hello!


I've heard sometimes, that it isn't a good
decission to boot your OS directly from a SAN
(Windows or Linux in my case)

Can you tell me if this is really true?

Thanks for your help!


Best Regards,
chris



If you are booting several "similar" systems,
it can be a very good idea to boot from the SAN,
especially if your SAN storage supports things
like lots of read-only, read-write and full copies.

One of the benefits is server change management.
If you are interested you can see a description
in this document from 3par:
http://www.3par.com/documents/april_...mt_OP_01.1.pdf

summary from their web site:
"Managing new patches, releases, and parameters for operating
systems and applications across multiple servers is laborious,
error-prone, and capacity intensive. 3PAR solves this problem
by allowing users to maintain a few "golden boot" images and
to distribute these tested images to countless servers using
space-efficient read-write snapshots. Users gain a highly
centralized, scalable solution with inimical capacity. The
combination of space-efficiency, writeability, and the number
of images that can be stored and distributed make this proven
solution completely unique."

-nw

In article k.net, THop wrote:
The main reason I recommend having the swap and boot disks on SAN and
not DAS is for availability. If the internal disk fails, the system is
down and therefore whatever app is running on it. Even if you have
mirrors in the internal disk many systems require shutdown to replace
those disk, especially when it is scsi. The OS is just as valuable as
your application... Without it, your app is dead anyway..
THop

netwuffus wrote:

Christian Reiter wrote in message . ..

Hello!


I've heard sometimes, that it isn't a good
decission to boot your OS directly from a SAN
(Windows or Linux in my case)

Can you tell me if this is really true?

Thanks for your help!


Best Regards,
chris



If you are booting several "similar" systems,
it can be a very good idea to boot from the SAN,
especially if your SAN storage supports things
like lots of read-only, read-write and full copies.

One of the benefits is server change management.
If you are interested you can see a description
in this document from 3par:
http://www.3par.com/documents/april_...mt_OP_01.1.pdf

summary from their web site:
"Managing new patches, releases, and parameters for operating
systems and applications across multiple servers is laborious,
error-prone, and capacity intensive. 3PAR solves this problem
by allowing users to maintain a few "golden boot" images and
to distribute these tested images to countless servers using
space-efficient read-write snapshots. Users gain a highly
centralized, scalable solution with inimical capacity. The
combination of space-efficiency, writeability, and the number
of images that can be stored and distributed make this proven
solution completely unique."

-nw

I agree with many of your points. However for AIX specifically
there is no need to power off the server to replace the mirrored
internal OS/swap drives. All these systems are hot swap. Sorry,
all the new versions of the hardware are hot swap (the p630
and above servers).

Mike