Filesystems (ext3, reiser, xfs, jfs) comparison on Debian Etch (Debian Administration) [LWN.net]

Filesystems (ext3, reiser, xfs, jfs) comparison on Debian Etch (Debian Administration)

Posted May 6, 2006 13:56 UTC (Sat) by anton (subscriber, #25547)
In reply to: Filesystems (ext3, reiser, xfs, jfs) comparison on Debian Etch (Debian Administration) by dlang
Parent article: Filesystems (ext3, reiser, xfs, jfs) comparison on Debian Etch (Debian Administration)

>hard drive that allows you to disable the write cache on it (i.e. no
>IDE drives qualify).

hdparm -W0 works on any IDE drive I have tried it on (and we run all
our ext3 FSs without disk write caches).

>since there is a huge performance penalty for doing this

Well, I recently tried it:

Disk: SAMSUNG SV1204H, ATA DISK drive
FS: ext3
Task: writing a 4.3GB file
Time: 12 min without write caching
6 min with write caching

So the penalty was a factor of 2 in this case.

>as an excercise consider how many seeks could be required to write all
>the data in a 16M buffer, and how long that could take.

The drive could have a 16MB spare area for just this case, and dump
the buffer contents there; it could read that area on powerup, and
then proceed as if there had been no power outage (i.e. write the
blocks to their home location). On a modern drive, this would take
0.25s. So it's not impossible, but I don't believe it is being done.

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