[lustre-discuss] how to optimize write performances

[Degremont, Aurelien]

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-bounces at lists.lustre.org au nom de riccardo.veraldi at cnaf.infn.it> a écrit :

    CAUTION: This email originated from outside of the organization. Do not click links or open attachments unless you can confirm the sender and know the content is safe.



    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



    _______________________________________________
    lustre-discuss mailing list
    lustre-discuss at lists.lustre.org
    http://lists.lustre.org/listinfo.cgi/lustre-discuss-lustre.org