For every one who is interested here is 2 posts about HDPARM, the second one
is from the Developer of this utility, Mark Lord.
[»] Do NOT enable -W1! DO USE -W0 instead!
by MA - May 29th 2002 08:47:05
The -W1 switch enables the write cache of a hard disk and will cause severe
file system corruption in face of a power outage that occurs while a write
operation is in progress. Journalling file systems (reiserfs, ext3fs, xfs,
jfs, you name it) cannot help about this either, but may instead hide the
actual problem. These file systems rely on their write operations being
performed in order.
However, most IDE drives ship with write caches enabled to cheat benchmarks,
at the expense of data safety.
Use hdparm -W0 on all your drives to turn the write cache off.
If your drive supports tagged command queueing, it will help write
performance as soon as support for this feature gets into your kernel. Tagged
Command Queueing makes the write cache safe.
Write barrier support patches are also circulating and may help safety, but
before these are in you kernel, enabling the write cache or leaving it
enabled without using tagged command queueing is UNSAFE.
You have been warned.
[»] Re: Do NOT enable -W1! DO USE -W0 instead!
by Mark Lord - May 29th 2002 09:09:28
There is small (VERY SMALL) potential for losing a disk write on sudden
powerfail with the drive caching enabled. But this is so small as to be
insignificant for nearly all of us, and enabling the write cache does FAR
MORE than just "cheat benchmarks" -- it really does improve system response
and throughput quite noticeably. I use -W1 continuously during kernel
development, with extremely frequent crashes and have never, ever, lost even
a sector of data. So while the possibility exists, say about the same as
contracting a flesh-eating disease, in reality -W1 is safe for the rest of
us, and really speeds up the system. The poster above is more than welcome
(hey, even encouraged!) to stick with the slow -W0 lifestyle. But life is too
short for me to wait that much for my computer. Cheers
The warning has been given...
Chainy
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