From: <Chris.Phillips_at_email.protected>
Date: Tue, 25 Aug 2009 16:15:37 +1000

Yes but the problem with ext2 is that if the disk is uncleanly
unmounted you have to wait ages to run fsync.

xfs seems to be the speed of ext2 and not the problems. Reformatting
changes are a trivial change to the scripts.

Cheers
Chris

On 25/08/2009, at 4:12 PM, Claire Hotan wrote:

>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
>
>
>
>
>

------------------------------------------------------------
Chris Phillips
CSIRO ATNF eVLBI project scientist
Office: (+61) (0)2 93724608 Mobile: (+61) (0)439487601
Received on 2009-08-25 16:15:58