Re: 2.3.x wish list?

Malcolm Beattie (mbeattie@sable.ox.ac.uk)
Thu, 13 May 1999 16:26:39 +0100 (BST)


David S. Miller writes:
> Date: Wed, 12 May 1999 09:14:17 -0400
> From: <mark@hoist.nlcomm.com>
> - ext2 is showing its age on larger partitions; my 3 9 gig drives
> take about a half hour to fsck, and up to a minute just to mount.
> My database server will need support for +2gig files by the end
> of the year. "go to a 64 bit machine" is not reasonable for
> everyone. 8^)
>
> Solved by Stephen Tweedie's ongoing logging filesystem work.

Even without that, the performance of fsck (and mount, come to that) is
massively improved by doing a mke2fs with 4k blocks instead of 1k.
Here are some figures I sent to linux-raid a few months ago:

Hardware: 350 MHz Pentium II PC, 512 MB RAM, BT958D SCSI adapter.
Sun D1000 disk array with 6 x 9 GB 10000 RPM disks.
Software: Linux 2.0.36 + latest RAID patch.
Filesystem configured as a single 43 GB RAID5 ext filesystem with
4k blocks and 64k RAID5 chunk-size.

I created 25 subdirectories on the filesystem and in each untarred
four copies of the Linux 2.2.1 source tree (each is ~4000 files
totalling 63 MB untarred).

fsck took 8 minutes.

Then I added 100 subdirectories in each of those subdirectories and
into each of those directories put five 1MB files. (The server is
actually going to be an IMAP server and this mimics half-load quite
well). The result is 18 GB used on the filesystem.

fsck took 10.5 minutes.

Then I added another 100 subdirectories in each of the 25 directories
and put another five 1MB files in each of those. The result is 30 GB
used on the filesystem.

fsck took 13 minutes.

The upshot is that although it's not as fast at fscking as a
journalled filesystem, with 4k blocks it's adequate for many more
uses than you'd expect if you stick with the default 1k blocks.
(This is separate from the current 2GB VFS limit on 32-bit
architectures of course.)

--Malcolm

-- 
Malcolm Beattie <mbeattie@sable.ox.ac.uk>
Unix Systems Programmer
Oxford University Computing Services

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