Re: SCSI or IDE
On Sun, Nov 24, 2002 at 12:38:56PM -0500, Scott wrote:
> After some talks with the person who handles the books she has given me
> the authority to bail on these Netfinity boxes and get something more
> supported by Debian. My question is: with IDE drives as fast as they are
> now does it really pay to go SCSI? Are there any benefits besides RAID?
> I understand fault tolerance, but how about performance?
I have used SCSI and IDE in many levels of the game. I've also used
filers (Netapp).
I currently work with an ISP that has mostly IDE on the servers doing
miscellaneous stuff, all SCSI RAID5 on the servers such as database, NFS
and network monitoring. I just like being able to pull a drive hot and
replace it nice and easy in the servers that are most critical to me.
There's quite little point in having IDE for my work on the most mission
critical servers. We also have a habit of netbooting many of our
machines. POP/SMTP/HTTP/HTTPS/DNS are done via netboot. This reduces our
reliance on drives in tons of systems. I would be happy to know if there
are controllers and setups that allow hotswappable IDE RAID5 - I'd be
very interested if there were (please feel free to let me know on or off
list).
At home, where we have a completely overbuilt network (geek!) I have a
server with IDE software RAID1 (dual 40G) and a SCSI RAID5 array that is
external and on a module installed basis so I can move/add/remove
drives at will - without losing my uptime on the main machine. My SCSI
array is currently 54G, but will expand again in the spring when I make
some other upgrades and free up more like drives. I also like to add and
remove my SCSI CD-ROMs as well, just cause I have several laying around.
I've seen (figuring off the top of my head) a 3:1 IDE/SCSI failure rate
across all drives/servers/systems. I'm not recalling that many failures
all told. I can actually only recall two SCSI failure, a 2G WD and a 18G
IBM. I've had multiple Fujitu IDE, WD IDE failures, sometimes with the
replacement drive failing in the same machine (Grrr)
Overall, this would be my recommendation (IMHO - YMMV)
IF you can get a combination of good IDE drives with good IDE
controllers that don't peg your CPU usage and money is an issue, go with
IDE. Never put two RAID1 IDE drives on the same channel (primary or
secondary). Put one on each for safety. For storing mp3's at home or
files locally, IDE is generally well suited and will save you a lot.
If you've got more money and want to see a (actual, not spec) better
MTBF, go with SCSI. Take the time to learn how SCSI works, terminations,
etc. Research block sizes on RAID arrays. Experiment to get the best
speeds. Use multiple controllers if you want. Have proper cooling.
I think SCSI edges out IDE for reliability and I think the extra cost is
worth it. And if your data is super mission critical, just buy a filer
instead and use snapshots. If, as I reread your question, you just want
to know "Is SCSI worth it for speed?" - no, probably not, you can do
well with an intelligently configured IDE system.
$.02, FWIW,
John
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