The question you really have to ask about PTT is if your media servers are
capable of handling the I/O or not (for the duplication jobs from the DXi7500
to tape), and it's really a question of if you are pushing your tape drives
fast enough to fully utilize them. If you need help in this area, I'd say it's
defiantly worth it as it will remove that I/O from the media server and put it
directly on the DXi7500, were its going to have to be either way anyway.
The other question is about loosing a fiber connection. I have no problem
loosing one of the fiber connections for it because the other three give me
more than enough bandwidth for my needs. I actually wish I could have two of
them for it, or decide which one gets used for it (they force you to use FC6),
incase something fails and I need to failover to a different connection.
The one thing that bugs me the most about Path-to-Tape is I have no visibility
into threw-put speeds on that fiber path that gets dedicated to it because it's
not going threw any servers I can use to see it, my switched don't seem to
report it with near enough detail to be sure, and it's not getting reported by
the DXi7500 either (they're working on it they tell me).
NetBackup also says SSO isn't supported on the target drives used for PTT,
which means you have to dedicate physical drives to PTT; however, I've used it
with SSO just fine on 6.5.2. I shut it off after going to 6.5.3 because of
some bugs in NetBackup, but plan to turn it back on in 6.5.4 were those known
bugs are fixed (I'll find out for sure next week after the upgrade). You'll
defiantly want to make sure you dedicate some virtual drives on the DXi to
PTT/NDMP.
As for advantages, I haven't really seen any, but then I have some fairly beefy
media severs and without visibility into the thru-put it's really a guessing
game. Duplications don't seem any slower or faster (as long as I'm doing them
from QBFS/stating/cache), but how much of a difference it it is impossible to
tell for sure.
The only weird thing from a NetBackup perspective, is how it works with NDMP
(yes you have to have NDMP for NetBackup to use PTT), in that it assigns the
media to the DXi7500 as if it was the media server residence for the tapes
written with it. It make me wonder how well restores will work with that
configuration. I guess I need to test that more, but for now I just have a
script that re-assigns them to another media server.
I'm using the Master as both my Vault/duplication and NDMP/PTT server, and it
seems to work fine that way; especially with PTT so the I/O load isn't actually
on the master. You get the same efficiencies with PTT as you would get with
using a dedicated server for duplications, except that you don't have to buy
another server.
smpt wrote:
> Hi,
> May I ask, are you satisfied with the Path to tape option? It is worth to
> loose one fiber optic to do the duplications?
> As I see it, having one dedicated media server for duplication and not using
> one dedicate fiber for path to tape is more efficient.
>
> What I like at DXi7500 id the ability to duplicate to another DXi with the
> knowledge of NBU (with the latest firmware.)
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