Re: Bad performance when accessing a lot of small files

* Alexandre Biancalana <biancalana@xxxxxxxxx> [071221 12:48] wrote:
On 12/21/07, Alfred Perlstein <alfred@xxxxxxxxxxx> wrote:

Hi Alfred !


There is a lot of very good tuning advice in this thread, however
one thing to note is that having ~1 million files in a directory
is not a very good thing to do on just about any filesystem.

I think I was not clear, I will try explain better.

This Backup Server has a /backup zfs filesystem of 4TB.

Each host that do backups to this server has a /backup/<hostname> and
/backup/<hostname>/YYYYMMDD zfs filesystems, the last contains the
backups for some day of that server.

My problem is with some hosts that have in your directory structure a
lot of small files, independent of the hierarchy.

Can you not tar these files together?

One trick that a lot of people do is hashing the directories themselves
so that you use some kind of computation to break this huge dir into
multiple smaller dirs.

I have the two cases, when you have a lot of files inside on directory
without any directory organization/distribution but I also have
problems with hosts that have files organized in a hierarchy like
YYYY/MM/DD/<files> having no more that 200 files in the day directory
level, but almost one million of files in total.

Just for info, I made the previous suggested tuning (raise dirhash,
maxvnodes) but this improve nothing.

Thanks for your hint!

What application are you scanning these files with? I know I had
issues with rsync in particular where I had to have it rsync
smaller pieces of a collection for it to work nicely instead of
going for the whole heirarchy.



--
- Alfred Perlstein
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  • Re: Bad performance when accessing a lot of small files
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