[mapserver-users] RE: To SCSI or not ?

[Matt.Wilkie]

> The way I understand it, IDE uses a lot of CPU time if you have 
> many requests, SCSI uses next to none.. on one of our servers 
> (file/print/terminal) we have a 4-drive SCSI array and one 80 
> GB IDE drive for temporary storage... when anyone transfers 
> large amounts of data to/from the IDE drive, the terminal 
> services sessions start to hang-- and this is a dual-CPU machine.

SCSI is definately better, but if the SCSI price tag is simply 
too much you can get add on IDE RAID cards which will off-load 
most of the work from the CPU. Some new motherboards also come 
with embedded IDE-RAID controllers. Note that Software RAID is
slower than Hardware RAID, make sure you know which one is 
being offered.

Not all IDE cards are created equal: search the newsgroups for 
problems on the particular model(s) you are interested in. Also
check the combinations, sometimes an otherwise reliable card
just won't work well with a particular motherboard or chipset.
Promise seems to be one of the most reliable brands (or at least 
one with best mindshare).

For an article which tells you way more than you ever wanted to
know see (page 6 of 30) 
http://www.anandtech.com/storage/showdoc.html?i=1491&p=6
If you aren't a hardware nut there are companies who sell boxed
IDE RAID solutions.

Search Keywords: IDE|SCSI RAID, JBOD (Just a Bunch Of Disks), 
SAN (Storage Area Network), NAS (Network Attached Storage).

Bottom line: if the server is likely to be around for awhile
and you haven't purchased it (or all the drives) yet, go with 
scsi and take the time to plan/research everything out.

If you already have a server in production with IDE drives, try 
a cheap test: buy a two drive IDE drive controller (ATA66 or 
better) and see what happens. The card shouldn't set you back
more than $100US.


cheers,

-matt

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Matt Wilkie * Yukon Renewable Resources GIS
http://renres.gov.yk.ca/pubs/rrgis/
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