Hello
To achieve higher throughput with a single threaded process, you should try to
limit latencies and parallelize under the hood.
Try checking the following parameters:
- Stripe your file across multiple OSTs
- Do large I/O, multiple MB per write, to let Lustre send multiple RPC to
different OSTs
- Try testing with and without Direct I/O.
What is your 'dd' test command?
Clear and check rpc stats (sudo lctl set_param osc.*.rpc_stats=clear; sudo lctl
get_param osc.*.rpc_stats). Check you are sending large RPCs (pages per rpc).
Aurélien
Le 30/09/2021 18:11, « lustre-discuss au nom de Riccardo Veraldi »
<lustre-discuss-boun...@lists.lustre.org au nom de
riccardo.vera...@cnaf.infn.it> a écrit :
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Hello,
I wanted to ask some hint on how I may increase single process
sequential write performance on Lustre.
I am using Lustre 2.12.7 on RHEL 7.9
I have a number of OSSes with SAS SSDs in raidz. 3 OST per oss and each
OST is made by 8 SSD in raidz.
On a local test with multiple writes I can write and read from the zpool
at 7GB/s per OSS.
With Lustre/ZFS backend I can reach peak writes of 5.5GB/s per OSS which
is ok.
This anyway happens only with several multiple writes at once on the
filesystem.
A single write cannot perform more than 800MB-1GB/s
Changing the underlying hardware and moving to MVMe slightly improve
single write performance but just slightly.
What is preventing a single write pattern to perform better ? They are
XTC files.
Each single SSD has a 500MB/s write capability by factory specs. So
seems like that with a single write it is not possible to take advantage
of the
zpool parallelism. I tried also striping but that does not really help much.
Any hint is really appreciated.
Best
Riccardo
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