[Gluster-users] Write performance tragically slow

[Pavel Snajdr]

So is it the scheduler in the kernel to blame?

Do you really think this is the issue? So if FUSE is that bad, is 
Gluster team working on kernel module?
Or is this an issue, that will not be solved?

On 18.11.2010 15:41, Anand Avati wrote:
> FUSE based filesystems have to face the unfortunate overhead of context
> switches between application and the filesystem process. GlusterFS does
> aggregate small writes but the aggregation code lies beyond the context
> switch hill. Nothing much can be done about it. We do however expose
> stbuf.st_blksize to be 128KB which applications like 'cp' honor and
> perform IO with that block size.
>
> Avati
>
> On Mon, Nov 15, 2010 at 8:19 PM, Pavel Snajdr <snajpa at snajpa.net
> <mailto:snajpa at snajpa.net>> wrote:
>
>     I played with it further after I wrote that e-mail and I found out,
>     that this interesting thing:
>
>     dd if=/dev/zero bs=X count=10000
>
>     X       troughput
>     1k      ~3MB/s
>     2k      ~6MB/s
>     4k      ~12MB/s
>     8k      ~24MB/s
>     16      ~48MB/s
>     ...
>     128k    110MB/s
>
>     => meaning I have tragically low IOPS (+- according to my 0.030ms
>     network latency).
>
>     Gluster config was one generated by "gluster" command (version
>     3.1.0), but I've tried either latest 3.0.x, resulting the same.
>
>     I've tried probably all performance translators available, even AFR
>     instead of replicate.
>
>     Is there any way to aggregate the writes and propagate them to the
>     network in bigger chunks, ie. 128k?
>
>     What I don't understand is how for example NFS does this? With NFS
>     there is no such problem and even though IOPS are slig
>
>
>     On 15.11.2010 14:22, Luis E. Cerezo wrote:
>
>         have you tried larger files? I have seen a note somewhere that
>         refers to tons of itty bitty files, it even cites the kernel
>         source as an example. I can't seem to find it.
>
>         Could you try larger than 1k files?
>
>         -luis
>
>
>
>
>         On Nov 10, 2010, at 8:23 PM, Pavel Snajdr wrote:
>
>             Hello,
>
>             I imagine you get this kind of messages all the time, but
>             just in case:
>
>             I have setup with 2 storage servers with debian package of
>             gluster - version 3.1.0
>
>             They are connected by dedicated 1 gigabit ethernet cards.
>
>             I've set up simple replicated storage with 2 replicas and
>             transport over TCP (just followed the how to on the wiki
>             with obvious changes).
>
>             Here goes my problem:
>
>             If I try to copy small files (i.e. extract kernel source) I
>             get a horrible results:
>
>             praha-storage2:/mnt/test# time tar xf linux-2.6.26.8.tar.bz2
>
>
>             real 15m19.825s
>             user 0m13.989s
>             sys 0m5.152s
>
>             likewise when rsyncing OpenVZ VPSes - I just can't get over
>             2MB/s in syncing.
>
>             I've monitored all resources - CPU load, network, disk I/O -
>             they are all used up to 0.00000nothing %.
>
>             Network latency is about 0.11 ms all the time.
>
>             Is this normal, or am I doing something wrong?
>
>             Please help. I am frustrated :(
>
>             --
>             S pozdravem / Best Regards
>
>             Pavel Šnajdr
>             +420 720 107 791
>
>             http://vpsfree.cz
>
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>
>
>         Luis E. Cerezo
>
>         blog: http://www.luiscerezo.org
>         fotofun: http://www.flickr.com/photos/luiscerezo/
>         twitter: http://twitter.com/luiscerezo/
>         Voice: +1 412 223 7396
>
>
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