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List:       bacula-users
Subject:    Re: [Bacula-users] Multiplexing multiple jobs to tape
From:       Justin Piszcz <jpiszcz () lucidpixels ! com>
Date:       2007-09-03 12:52:52
Message-ID: Pine.LNX.4.64.0709030852440.17135 () p34 ! internal ! lan
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On Mon, 3 Sep 2007, Chris Howells wrote:

> Hi John,
>
> John Drescher wrote:
>>> I believe the 120MB/s is the raw speed, 240MB/s is the compressed speed.
>>>
>> I tried to check on that but I did not find the direct answer. But I
>> did find an article by IBM that stated that LTO4 did 120MB/s while
>> LTO3 did 80MB/s. So I went to my tape vendor's web site and it stated
>> that the 80MB/s for LTO3 was compressed with 40MB/s native so I came
>> to the conclusion that the 120MB/s number was the compressed number...
>
> Ah, you may well be right, I was in a rush and was using such reliable
> sources as Wikipedia ;)
>
> I'll try and get a more definitive answer.
>
>> You are correct. That is why I test with actual data from a raw partition.
>>
>> Is this a SCSI tape drive? You might want to check on the speed it is
>> communicating at (possibly stuck in LVD 80MB/s mode)...
>
> It's actually SAS, so I don't believe that can be the problem.
>
> Anyway, FWIW, I temporarily hooked the drive (with the same LSI SAS
> controller) up to a dual 3GHz Core 2 Duo. Got 91MB/s rather than 80MB/s
> writing zeros to the disk with dd, so the old Opteron does seem to be a
> tad lethargic.
>
> Anyway, I've got multiplexing working, so I'm going to try backing up
> three clients tomorrow and see what kind of performance I get. I expect
> it will suck but we'll see :)
>
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Bacula now supports multiplexing?


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