Hello Preston,
this is the line used dd if=/dev/zero of=$1 bs=32k count=32768
so block size is 32k and 32768 blocks to have 1 GB
the dedicated interface is a LP9802 emulex 2Gbs HBA, so normally this may not
be the bottleneck.
Bart
-----Original Message-----
From: Legato NetWorker discussion [mailto:NETWORKER AT LISTSERV.TEMPLE DOT EDU]
On Behalf Of Preston de Guise
Sent: Thursday, May 04, 2006 2:20 PM
To: NETWORKER AT LISTSERV.TEMPLE DOT EDU
Subject: Re: [Networker] maximum speed to tape using bigasm and /dev/zero
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
> respond to Preston de Guise <enterprise.backup AT GMAIL DOT COM> All email is
> logged and may be reviewed - Refer policy FP206
>
> To
> NETWORKER AT LISTSERV.TEMPLE DOT EDU
> cc
>
> 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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