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Date:      Thu, 01 Jan 2004 17:59:18 -0500
From:      Scott W <wegster@mindcore.net>
To:        Scott Mitchell <scott+freebsd@fishballoon.org>
Cc:        freebsd-questions@freebsd.org
Subject:   Re: What do you use?
Message-ID:  <3FF4A646.2020808@mindcore.net>
In-Reply-To: <20040101224616.GA4891@tuatara.fishballoon.org>
References:  <3FF31E4B.1070305@edgefocus.com> <200312311706.25677.jbacon@mcw.edu> <3FF35827.8000500@edgefocus.com> <20040101114640.GB675@tuatara.fishballoon.org> <20040101130752.V65501@zoraida.natserv.net> <20040101224616.GA4891@tuatara.fishballoon.org>

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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
>>documents/spreadsheets).
>>    
>>
>
>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, 
$^#&*(
;-)

Scott

>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.
>

>	Scott
>
>  
>




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