[Date Prev][Date Next]   [Thread Prev][Thread Next]   [Thread Index] [Date Index] [Author Index]

Re: [K12OSN] Knowledge turned crisis

I don't recall how many users Liam said he has, but one concern I would have about using IDE drives is that they have performance problems when you get above ten users or so on the terminal server. We've discussed this before, a year or so ago. The consensus seemed then to be that one could use IDE drives with small labs, but beyond 10 users, SCSI's ability to re-order requests made for much more efficient access to the disk. And I think SATA addresses that to some degree, although still not as well as SCSI as I recall. But perhaps doing RAID 0 makes this less of an issue (?). Anyone's thoughts?


Les Mikesell wrote:
From: David H. Barr

If you're going to stick with EIDE, you don't necessarily need more than one card; Typically for low-end setups I set one hdd as master0, and a dvd/cdrw as slave0. Then 3 drives go in, one as master1, master2, master3 -- and voila! Cheapest raid5 w/hotspare I know how to get ahold of. Essentially you want to make sure they have their own CHANNEL, not necessarily their own controller.

I haven't measured this but I'd expect it to cut write performance
in half if you mirror 2 IDE drives on the same controller.  Unlike
SCSI, the IDE controllers can only handle one outstanding command
at a time so writes to two drives on the same cable won't run
in parallel.  Software raid5 slows you even more because the CPU
gets involved and you force all the drive heads to seek at once
instead of independently.

As long as one is doing software raid, though, what's the problem with SATA drives? A generic controller is less than $30, and you can get 80GB models for dirt cheap.

SATA forces you to use only one drive per controller although you
can get cards with more than 2 controllers.

   Les Mikesell
     les futuresource com

K12OSN mailing list
K12OSN redhat com
For more info see <http://www.k12os.org>

[Date Prev][Date Next]   [Thread Prev][Thread Next]   [Thread Index] [Date Index] [Author Index]