Hi Bart,
When running dd from /dev/zero, what bs=x argument are you using? I'd expect
a lower performance such as you're citing if you didn't specify a block size
argument. Aim for an absolute minimum of 32k, go up to 256k to see whether
this changes your performance.
If it doesn't, you could very well be hitting maximum throughput speed for
the interface.
Cheers,
Preston.
On 5/2/06, Jespers, Bart <Bart.Jespers AT fujitsu-siemens DOT com> wrote:
Hello All,
thanks for the answers concerning bigasm. I agree that 45-55MB/s is good
on LTO2
however if you use dd comming from /dev/zero (creates only zero's), the
compression should be the highest possible since zeroes are very good
compressable.
however we also see a max speed of 45-55MB/s using /dev/zero.
does anybody has tested this?
bart
-----Original Message-----
From: Legato NetWorker discussion [mailto:NETWORKER AT LISTSERV.TEMPLE DOT EDU]
On Behalf Of Matthew Robert
Sent: Tuesday, May 02, 2006 2:47 AM
To: NETWORKER AT LISTSERV.TEMPLE DOT EDU
Subject: Re: [Networker] maximum speed to tape using bigasm and /dev/zero
This email is to be read subject to the disclaimer below.
My personal best is 189MB/sec on LTO3 backing up a mix of file & print
data and some big SQL dbases at once.
Im going to give bigasm a run to see how well it runs..
Cheers,
Matt
Preston de Guise <enterprise.backup AT GMAIL DOT COM> Sent by: Legato NetWorker
discussion <NETWORKER AT LISTSERV.TEMPLE DOT EDU>
02/05/2006 10:34 AM
Please respond to
Legato NetWorker discussion <NETWORKER AT LISTSERV.TEMPLE DOT EDU>; Please
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Subject
Re: [Networker] maximum speed to tape using bigasm and /dev/zero
Typically running bigasm against IBM LTO-2 tape drives on Solaris hosts I
have seen a peak speed of around 42MB/s. On the whole, bigasm does generally
represent a nice level of compression without going overboard.
On the second general question of "what speed have you obtained", the best
yet remains an LTO-1 tape drive which ran at around 98MB/s backing up heaps
of holey SQL databases...
Cheers,
Preston.
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