Scott Mitchell wrote:

On Thu, Jan 01, 2004 at 01:09:23PM +0000, Francisco Reyes wrote:

On Thu, 1 Jan 2004, Scott Mitchell wrote:

As for RAID, we use Vinum, but only because I inherited a bunch of machines
with hot-swap SCSI bays and no hardware RAID. It works well, once you have
it set up, and I've even managed to swap out failed drives without a reboot
:-) I'll definitely investigate the 3ware cards when I need to build a new
RAID server, though.

But wouldn't a 3ware RAID be slower than an SCSI setup? Unless your
current setup is using old SCSI disks. Also how is the load? Lots of
simultaneous use or just many quick/small access (ie people using

There no particular reason for an ATA RAID to be slower than SCSI, assuming similar disks in each. 10krpm 'server class' ATA disks are available these days, although I don't know that anyone has done a 15krpm one yet.

Does SATA have tagged queing? (I don't know offhand if it does...?)

I can guarantee modern SCSI throughput is superior to any of the SATA drives I've seen to date. Several of the 'hardware sites' (I think Tomshardware did a writeup on this or anadtech among others) agree with this statement as well. ATA specs tend to exaggerate their capabilities even worse than SCSI specs do- burst speeds are all fine and dandy, but not realistic at all in the real world. Meaning basically in short I wouldn't choose SATA over SCSI for a production server of any kind where speed was an issue. ATA has gotten better by far than it was speed-wise, and I'd be OK with it on a personal workstation for any purpose, but it's still playing catchup.

In any case, performance is only one reason to use RAID.  My arrays are
RAID-5's, serving developer home directories over NFS, and a CVS server
(ie. lots of small file accesses).  The main requirements were to have
some fault tolerance and to get the most out the of disks I could buy with
the available budget - hence the RAID-5.  Read performance is no worse than
with a single disk, and degrades more gracefully with multiple simultaneous
access.  Write performance is pretty awful, but that's the nature of
RAID-5.  No doubt if I had an unlimited budget I would do things
differently, but those days are long gone :-(

Write performance is awful locally, or over NFS? NFS isn't exactly a speed demon.
No comment on the unlimited budget as everyone at work just got (another) 'mandatory pay reduction'...but I do rememeber and miss those, $^#&*(


I'd also expect/hope that a hardware solution (ATA or SCSI) would be easier
to manage.  Vinum is great, but swapping out a dead drive is still a scary,
multi-step procedure, that I do infrequently enough that it always requires
half an hour with the manual and my notes from last time to make sure I get
it right.  With our Windows servers (Compaq Proliants with hardware RAID),
you just yank the old drive, plug in the new one, and it's done.  I'd love
to be able to do that with the FreeBSD servers as well.


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