[Lustre-discuss] Slow Directory Listing

[Indivar Nair]

I have 1 OST Per OSS.
I have set the stripe to Lustre default. Should I still change the stripe
count to 1?
Yes, the reads are sequential.

1. Will increasing / decreasing the number of max_rpcs_in_flight help?
It is set to 32 now.

2. Just for experimenting, would it speed up listing if 1 OSS served 2 OSTs,
thereby reducing the number of OSS and RPCs?

Regards,


Indivar Nair

On Wed, Sep 7, 2011 at 1:28 AM, Adrian Ulrich <adrian at blinkenlights.ch>wrote:

>
> > While normal file access works fine, the directory listing is extremely
> > slow.
> > Depending on the number of files in a directory, the listing takes around
> 5
> > - 15 secs.
> >
> > I tried 'ls --color=none' and it worked fine; listed the contents
> > immediately.
>
> That's because 'ls --color=always|auto' does an lstat() of each file
> (--color=none doesn't) which causes Lustre to send:
>
>  - 1 RPC to the MDS per file
>  - 1 RPC (per file) to EACH OSS where the file is stored to get the
> filesize
>
> Some time ago i've created a patch to speed up 'ls' while keeping (most) of
> the colors
> (
> https://github.com/adrian-bl/patchwork/blob/master/coreutils/ls/ls-lustre.diff
> )
>
> But patching samba will not be possible in your case as it really needs the
> information returned by stat().
>
>
> > Double clicking on directory takes a long long time to display.
>
> Attach `strace' to samba: It will probably be busy doing lstat() which is a
> 'slow' operation on Lustre in any case.
>
>
>
> > The cluster consist of -
> > - two DRBD Mirrored MDS Servers (Dell R610s) with 10K RPM disks
> > - four OSS Nodes (2 Node Cluster (Dell R710s) with a common storage (Dell
> > MD3200))
>
> How many OSTs do you have per OSS?
> What's your stripe setting? Setting the stripe to 1 could give you a huge
> speedup (without affecting normal I/O as i assume that the 9MB files are
> read/written sequentially)
>
>
> Regards,
>  Adrian
>
>
> --
>  RFC 1925:
>   (11) Every old idea will be proposed again with a different name and
>        a different presentation, regardless of whether it works.
>
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