[Lustre-discuss] ldiskfs performance vs. XFS performance

Michael Kluge Michael.Kluge at tu-dresden.de
Mon Oct 18 04:58:40 PDT 2010


Hi list,

we have Lustre 1.8.3 running on a DDN 9900. One LUN (10 discs) formatted
with XFS shows 400 MB/s if oppressed with one 'dd' and large block
sizes. One LUN formatted an mounted with ldiskfs (the ext3 based that is
default in 1.8.3.) shows 110 MB/s. It this the expected behaviour? It
looks a bit low compared to XFS.

We think with help from DDN we did everything we can from a hardware
perspective. We formatted the LUN with the correct striping and stripe
size, DDN adjusted some controller parameters and we even put the file
system journal on a RAM disk. The LUN has 16 TB capacity. I formated
only 7 for the moment due to the 8 TB limit. 

This is what I did:

MDS_NID=IP at SOMEHWERE
RAM_DEV=/dev/ram1
dd if=/dev/zero of=$RAM_DEV bs=1M count=1000
mke2fs -O journal_dev -b 4096 $RAM_DEV

mkfs.lustre  --device-size=$((7*1024*1024*1024)) --ost --fsname=luram
--mgsnode=$MDS_NID --mkfsoptions="-E stride=32,stripe-width=256 -b 4096
-j -J device=$RAM_DEV" /dev/disk/by-path/...

mount -t ldiskfs /dev/disk/by-path/... /mnt/ost_1

Is there a way to push the bandwidth limit for a single data stream any
further?



Michael


-- 

Michael Kluge, M.Sc.

Technische Universität Dresden
Center for Information Services and
High Performance Computing (ZIH)
D-01062 Dresden
Germany

Contact:
Willersbau, Room A 208
Phone:  (+49) 351 463-34217
Fax:    (+49) 351 463-37773
e-mail: michael.kluge at tu-dresden.de
WWW:    http://www.tu-dresden.de/zih
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