Re: striping, etc.
On Fri, 20 Jun 1997, Rick Hawkins wrote:
:
:> > They will go on a machine with 3 200m ide drives, which will be a poor-man's
:> > server. My current thinking is to mount / on the first controller, and
:> > use the other pair as /usr on the second interface. /usr will be NFS
:> > exported. Or would I be better off putting the two /usr drives on
:> > separate controllers?
:>
:> I'd think it was better to mount them across separate controllers. With
:> seperate control and data lines, the kernel can issue two simultaneous
:> requests and get data from both at the same time. My understanding with
:> IDE (and EIDE) is that a single controller can only access a single
:> drive at a time and must wait for that request to finish before issuing
:> another.
:
:yes; that's the hitch with ide. On the other hand, we don't have spare
:scsis lying around :)
:
:The reason i'm hesitating to put them on separate controllers is that /
:is also on the first controller. Everything that gets nfs exported will
:come off /usr, and my concern is that massive hits to the portion that
:was slaved could leave / unaccesable to the host.
:
:
:> SCSI is a more sophisticated in that it allows a request to be issued
:> and then the bus to idle (for more requests or other data) until the
:> drive finishes processing the request and can blast back the data.
:
:> This is why SCSI is much better than EIDE when dealing with more than one
:> drive. (At least, this is my understanding... Somebody please correct
:> me if I'm wrong.)
:
:yes; exactly. I just wish we had scsis. Of coure, if this whole thing
:works, we may be able to get one . . .
:
On that linux-raid list I told you about, someone was discussing IDE
performance. Seems that with their testing, which may or may not have
been very accurate, that putting IDE disks on the same or seperate
controllers seemed to have very little difference in performance. I
suspect this has more to do with the crappiness of IDE than anything to
do with the md algorithms.
Given your concerns about / being accessable, I believe the best choice
would be to put both drives on the secondary controller. After all,
this is a proof of concept type install, right? I suppose you could try
creating a linear device and a raid0 device and run some adhoc tests to
see if there's a difference ... but I think you'll find that IDE is
holding you back, not the md stuff.
Good luck! May the gods grant you many gigs of SCSI disk :)
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