Andreas Micklei wrote:
Am Donnerstag, 10. Mai 2007 schrieb Feizhou:
Probably not, but is SATA really much worse then SCSI or SAS? I did
some testing on a dell PE 2950 of 750GB SATA's vs SAS and SCSI drives,
and the SATA drives seem to be faster at least at first glance. I don't
have good numbers from the SCSI tests, but at least for sequantial, I'm
getting a better speed off the SATAs.
sequential will be better than SCSI due to the packing on those platters
which make up for the lack in rpm. NCQ should even up the random ability
of SATA disks versus SCSI drives but that support has only become
available lately on Linux and you also need the right hardware (besides
the right disks).
SAS and SCSI really has it's place when you need random access with lots of
IOs per second, i.e. Fileserver, Database Server. We upgraded our Fileserver
(NFS, Samba) from SATA SW Raid to SCSI HW Raid and the difference is HUGE.
One the old system a single user doing a large file copy could bring the
system almost to a halt. On the new system you do not even notice if one user
does a similar operation. However plugging one of the same SCSI discs into
your average PC will not give you much advantage.
There is also a line of SATA discs that aim for the low-end server market, the
WD-Raptors. They spin at 10.000 rpm and give much better random access
performance than normal SATA drives. The price point is very attractive
compared to SCSI and SAS. Great alternative for a tight budget.
Here is my favorite site for comparing drives. Has nice background articles
too:
http://www.storagereview.com/
I've always wanted a dollars to dollars comparison instead of comparing
single components, and I've always thought that a bunch of RAM could
make up for slow disks in a lot of situations. Has anyone done any sort
of tests that would confirm whether a typical user would get better
performance from spending that several hundred dollars premium for scsi
on additional ram instead? Obviously this will depend to a certain
extend on the applications and how much having additional cache can help
it, but unless you are continuously writing new data, most things can
live in cache - especially for machines that run continuously.
--
Les Mikesell
lesmikesell@xxxxxxxxx
_______________________________________________
CentOS mailing list
CentOS@xxxxxxxxxx
http://lists.centos.org/mailman/listinfo/centos
