Benno Senoner writes:
> does anyone of you know how long it takes,
> to e2fsck (after an unclean shutdown) for example a soft-raid5 array of
> a total size of about 40-50 GB
> ( example : 6 disk with 9GB (UW SCSI) )
> assume the machine is a PII300 - PII400
>
> assume that the raid-array is almost filled with data (so that e2fsck
> takes longer)
>
>
> can times go up to 1h ?
I did some benchmarks last Wednesday for a thread on the server-linux
mailing list. Here's a cut-and-paste job:
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 important points are probably that (a) the disks are 10000 RPM
which helps random I/O and (b) the filesystem block size is 4k. Don't
even think about using a 1k block size on a large filesystem (unless
you have a really weird environment).
> Is it very unsafe to remove fsck at boot ?
Yes. You might as well leave it in since if the filesystem was
unmounted cleanly then fsck doesn't bother checking it fully and
continues straight on.
> what about checking /proc/mdstat at boot time and then determining if
> e2fsck should be run or not ?
> In theory if the array was shut down cleanly , the filesystem should be
> in a consistent status.
> please correct me in I am wrong .
That's wrong. The consistency of the array and the consistency of the
filesystem on it are two independent issues.
--Malcolm
--
Malcolm Beattie <[EMAIL PROTECTED]>
Unix Systems Programmer
Oxford University Computing Services
