Hi!
I have to answer on this....
On Fri, Sep 5, 2008 at 12:03 PM, Hemant Shah <hjrrs AT yahoo DOT com> wrote:
>
>
> --- On Wed, 9/3/08, Michael Galloway <mgx AT ornl DOT gov> wrote:
>
>> From: Michael Galloway <mgx AT ornl DOT gov>
>> Subject: Re: [Bacula-users] Backup of many many files
>> To: "Ryan Novosielski" <novosirj AT umdnj DOT edu>
>> Cc: bacula-users AT lists.sourceforge DOT net
>> Date: Wednesday, September 3, 2008, 11:03 AM
>> On Wed, Sep 03, 2008 at 11:59:49AM -0400, Ryan Novosielski
>> wrote:
>> > -----BEGIN PGP SIGNED MESSAGE-----
>> > Hash: SHA1
>> >
>> > Chris Howells wrote:
>> > > Michael Galloway wrote:
>> > >
>> > >> how does concurency work for tape libraries?
>> can i use spooling and concurrency?
>> > >> would that help? i've already got
>> spooling job (2GB segments) and attributes.
>> > >
>> > > You can use concurrency with tape, yes. I write
>> five concurrent jobs to
>> > > LTO-4. (I have an autochanger, but it's only
>> got a single LTO4 tape
>> > > drive in it).
>> > >
>> > > The bacula manual warns somewhat against using
>> concurrent jobs with
>> > > tape, but I've been using it for a year,
>> every restore has been 100%
>> > > perfect, and the restore speed is absolutely fine
>> for my needs, it's
>> > > pretty quick anyway.
>> > >
>> > > I'm not sure about spooling as I don't
>> use it but I understand it can
>> > > help to increase restore speed, but as I said, I
>> don't have a problem
>> > > with restore speed anyway.
>> >
>> > You should use spooling. I'm not 100% sure that
>> interleaving should even
>> > be allowed, as I've heard of some people having
>> strange things happening
>> > with it enabled. Also takes life off your tape head,
>> if I'm not mistaken.
>> >
>>
>> are there any recommendations on the size of the spool
>> segment?
>
> It depends on how much disk space you have, they are cheap nowadays.
Yes, but not every "cheap" hard drive will be able to give you the
throughput to keep the tape writing continuously, for example, a LTO-4
drive that I tested a few weeks ago, gave ~100MB/s write speeds, and
the server that had it attached only went up to 70MB/s hard drive read
speed (sequential).
So, I decided to use tmpfs, ~ 1.5GB (I only had 2GB available :( ).
I have read lots of posts stating huge spool size, but I'm not sure if
they tested they hard drive performance compared to the tape's
performance.
I know this has been previously discussed on the list (that's where I
got the idea of using tmpfs), but I thought it could be a good idea to
bring this issue to this thread.
I hope this helps somebody, sincerely,
Ildefonso Camargo
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