From: <C.Hotan_at_email.protected>
Date: Tue, 25 Aug 2009 14:12:51 +0800

Hi all,

Not necessarily relevant but Randall felt that xfs and raiding didn't get on as well as ext2, so our internal feelings here were to simply turn off the journalling option in the formatting script, thus returning things to ext2, which means no significant changes but a probable potential speed up.

I'd be interested to know which disk sets Jamie used, were they "reliable"? The older disks seem more inclined to producing bigbuff errors at high speed, though there's also been problems with Curtin 750s. In general ATNF or CURT 500s that haven't had any history of disk failures seem to be best able to cope with high speeds, but if we have some disk sets that are marginal, then maybe switching to ext2 would fix those problems.

Of course if people want to use xfs that's cool too, but from a scripts perspective switching to ext2 would involve virtually no work, and we know everything works just fine with ext2 because it's what we used until a year ago.

Just my two bob.

cheers

Claire

-----Original Message-----
From: owner-vlbiobs_at_atnf.<!--nospam-->csiro.au on behalf of Chris Phillips
Sent: Tue 8/25/2009 1:58 PM
To: Jamie Stevens
Cc: VLBI observers
Subject: Re: LBA recorder disk speed tests
Thanks for doing this

Of course these results show *any* of the filesystems can cope with
512 Mbps....

Maybe we should try xfs for the next session. First we would need to
try some tests such as swapping disks after recording etc.

Cheers
Chris

On 25/08/2009, at 3:48 PM, Jamie Stevens wrote:

>Hi all,
>
>I've completed some diskspeed tests on cavsi1 using ext3, ext2 and xfs
>filesystems. I did all tests using filesizes that would have been
>generated by an experiment running at 512 Mbit/s; some with 10s files,
>others with 60s files.
>
>I've attached two postscript files to this email. Each shows the
>results
>of the 9 tests I did, and each file corresponds to tests run on one
>side
>of the Xraid (all tests were performed on both Xraid sides to ensure
>consistency).
>
>The results show that ext3 is quite a lot slower than ext2 or xfs,
>even
>when tuned for performance. xfs has the highest average speed, with
>ext2
>not far behind. It doesn't appear that changing the filesize has much
>effect on the average speed the disks can sustain.
>
>One of the most important things is the minimum speed. The bigbuffer
>will start to fill if the speed falls below the required recording
>rate,
>and this will lead to bigbuf skips if the disks don't catch up in
>time.
>ext3 filesystems have a very low minimum speed, as do ext2 filesystems
>with 10s files. But with 60s files, both ext2 and xfs do not drop much
>below 500 Mbit/s, and xfs can keep its minimum rate up even with 10s
>files.
>
>cheers
>Jamie
>
><
>lba_speedtests_xraid0
>.ps.gz><lba_speedtests_xraid1.ps.gz><Jamie_Stevens.vcf>

------------------------------------------------------------
Chris Phillips
CSIRO ATNF eVLBI project scientist
Office: (+61) (0)2 93724608 Mobile: (+61) (0)439487601
Received on 2009-08-25 16:13:07