| Marc de Vries 2004-07-19, 7:45 am |
| On Mon, 19 Jul 2004 09:28:50 +0200, "Benno..." <0@0.invalid> wrote:
>Benno... wrote:
>
>
>I was thinking, the RAID5 drive consists of 6 disk. Normally the more
>spindles the better the performance but is this also true with those
>very small files? Could a large number of spindles have a negative
>performance effect?
More spindles also gives better performnance with those very small
files. The array controller then has the option to read multiple files
simultaneously from different spindles.
Especially with small files you should set the stripe size to the
maximum that the controller supports. So it already has the optimum
setting. (The idea behind that is that the small files are stored on
as few disks as possible, which will increase the chance that you can
read several files simultaneously)
But whatever you do, you might increase performance, but you will
never ever get large transferrates with small files.
The reason for that is the following: The time it takes to search for
that file on the disk and open it is very large in comparison to the
time it takes to transfer it.
The same might also happen on the network. I'm not sure what overhead
you get on small files in the network. But you might want to take a
look at what happens when you access those small files directly on the
server, compared to what happens when you access them over the
network.
Are you doing a lot of writing to the array controller? You have to
accept that writes will never be fast. Extra cache will not fix that.
And it might slow the the reads down a bit in such a way that on
average the user experience is slower.
I don't have personal experience with roaming profiles, but I'd guess
they require more read than write capacity. More cache in the array
controller might help. if you have the option to add more.
You could experiment with the cluster size, but I don't think that
that will help. The cause of the slow performance is the relatively
large seektime when accessing small files. And that doesn't change
when the clustersize is smaller.
I'm afraid that I can't think of much to improve the situation.
Basically the applications shouldn't create so many extremely small
files, because that will always hurt performance. (Your backup
software is probably not too happy about it either)
Marc
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