Re: SATA-performance: Linux vs. FreeBSD

Am Dienstag, 13. Februar 2007 00:31 schrieben Sie:
Martin A. Fink wrote:
I have to store big amounts of data coming from 2 digital cameras to disk.
Thus I have to write blocks of around 1 MB at 30 to 50 frames per second
for
a long period of time. So it is important for me that the harddisk drive
is
reliable in the sense of "if it is capable of 50 MB/s then it should
operate
at this speed. Constantly."

The good old handful of suggestions:

- Use a dedicated disc for the task.

I used a dedicated disk for this task. No one else besides the task is writing
to it!

- Use an empty disc so there is no fragmentation.

All tests were performed on empty disk!

- Buy a bigger disk, they have high bandwidths.

I have a flash disk from a manufacturer who grants me 48 MB/s. And FreeBSD as
well as Windows reach this value. Only Linux 2.6.18 is far away from it (42
MB/s)

- Buy a more "specialized" disc.

see above

for e.x.: Western Digital Raptor X(*) a 150GB, 10-KRPM S-ATA disc.
- Buy several discs and use RAID 0
or alternate between discs when writing.

What I have to build is an application for the International Space Station
ISS. I am limited with power and space. So If the disk is able to write
constantly 48 MB/s then the Operating System should do this!

- use XFS. AFAIK XFS has about the best "large file" and "high
bandwidth" characteristics.
- that with XFS you can preallocate the files doesn't seem relevant in
this case. It's more for the case that you write several files
simultaneously over a longer period of time.
- Write to one large file and separate the individual files later.

if you are sure that you don't get a power-failure:
- Disable Write-Barriers, especially on a logging-filesystem.
- Enable write-caching.
(hdparm doesn't appear to be able to do that with a SATA-disc, but
blktool appears to be able to)
The later has a good chance of corrupting your filesystem when you do
get a power-failure!!!



*:
I don't think you want something from the server-line,
SCSI/FibreChannel/...?
IIRC i read a something about the first 100MB/s disc with in the 15-KRPM
league.

Power consumption! See above.

Bis denn

The problem is: FreeBSD is fast, but lacks of some special drivers. Linux has
all drivers but access to harddisk is unpredictable and thus unreliable!
What can I do??
--
Real Programmers consider "what you see is what you get" to be just as
bad a concept in Text Editors as it is in women. No, the Real Programmer
wants a "you asked for it, you got it" text editor -- complicated,
cryptic, powerful, unforgiving, dangerous.



--
Dipl. Physiker
Martin Anton Fink
Max Planck Institute for extraterrestrial Physics
Giessenbachstrasse
85741 Garching
Germany
Tel. +49-(0)89-30000-3645
Fax. +49-(0)89-30000-3569
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