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Jose Ildefonso Camargo Tolosa wrote:
> 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:
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>>>> 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).

That's an interesting question. I'll have to take a look at my
configuration and see how I do.

> 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.

- --
 ---- _  _ _  _ ___  _  _  _
 |Y#| |  | |\/| |  \ |\ |  | |Ryan Novosielski - Systems Programmer II
 |$&| |__| |  | |__/ | \| _| |novosirj AT umdnj DOT edu - 973/972.0922 (2-0922)
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