Before making such a generalized statement, Roger, you have to take into account what it's being used for and the type of software that's accessing it.
I agree with you that buying a SAN just for general storage would be a waste, though. Our hospital software is made up of different modules such as ADM for admitting, Lab, OE for Order Entry, etc. By utilizing the SAN properly, users won't see a hit because ADM would be hitting one set of disks while OE might hit another (although their is a lot of access from one module to another). Paul Chinnery Network Administrator Mem Med Ctr -----Original Message----- From: Roger Seielstad [mailto:[EMAIL PROTECTED]] Sent: Friday, October 04, 2002 12:19 PM To: NT 2000 Discussions Subject: RE: Basic SAN question 3 LUNS still means that you're going to see contention on about 1/3rd of all operations. Granted, caching will cover some of that, but not all of it. Add a 4th lUN and you're pretty much guaranteed contention on 50% of all disk ops. This is the 'scalability' side of SANs that's never discussed, because SAN vendors don't want you to know the dirty little secrets of their trade. I think you're correct in not expecting the users to see a performance hit, and it also seems that you're already aware that the SAN isn't going to buy you a big performance gain, either. Roger ------------------------------------------------------ Roger D. Seielstad - MCSE Sr. Systems Administrator Inovis - Formerly Harbinger and Extricity Atlanta, GA > -----Original Message----- > From: Chinnery Paul [mailto:[EMAIL PROTECTED]] > Sent: Friday, October 04, 2002 11:38 AM > To: NT 2000 Discussions > Subject: RE: Basic SAN question > > > I agree but, realistically, one of the nice things of a SAN > is the ability > to create separate LUN's off of the same disks. > Also, as was explained to me by an EMC engineer, if you have > a RAID 1/0, > you can be writing to one set and reading off the other. > Now for us, our users wouldn't even notice the performance > hit. We're going > from direct-attached, 7500 rpm to a SAN with 15000 rpm > drives. Add to that, > we're putting in a gigabyte backbone and brand-new servers > (upgrading from > Pro200 duals to 1.3 duals) attached to a Cisco 4006 swtich. > Of course, we're not slicing it up with a half-dozen > different luns either. > Maximum we've got is 3. > > Paul Chinnery > Network Administrator > Mem Med Ctr > > > -----Original Message----- > From: Roger Seielstad [mailto:[EMAIL PROTECTED]] > Sent: Friday, October 04, 2002 7:51 AM > To: NT 2000 Discussions > Subject: RE: Basic SAN question > > > Chris, > > Most vendors will allow you to slice and dice a SAN array > into as many LUNs > of whatever size you want. Its absolutely the wrong thing to > do, but it > certainly can be done. > > Any time a phisical platter is partitioned, you're going to take a > performance hit - simply put, the heads can't be in two > places at once, so > if two systems are trying to access data which is physically > on the same > platter, but logically on different LUNs, there is head > contention, and one > of the two must wait for the other to finish "using" the > heads, and then pay > the additional price of a head seek across the platter to its > assigned set > of cylinders. > > In the case of your single 500GB RAID5 set in your SAN being > split into > 300/100/50/50, you have in reality created 4 partitions on > each spindle, > with 60%/20%/10%/10% split on each spindle. With a large > number of platters, > and larger stripe sizes, its theoretically possible to reduce > the chances of > contention within the SAN, but realistically speaking, > chances are there is > going to be some contention, and therefore some performance > hits associated > with managing your disks this way. > > Its one of the lies^H^H^H^H omissions commonly done in the > sales pitches of > the big storage vendors. > > ------------------------------------------------------ > Roger D. Seielstad - MCSE > Sr. Systems Administrator > Inovis - Formerly Harbinger and Extricity > Atlanta, GA > > > > -----Original Message----- > > From: Chris Levis [mailto:[EMAIL PROTECTED]] > > Sent: Thursday, October 03, 2002 2:07 PM > > To: NT 2000 Discussions > > Subject: Basic SAN question > > > > > > If you have a RAID-5 array of (let's say) 500GB, can you > > create LUNs of an > > arbitrary size to be presented to the servers? E.g, a 300GB, > > a 100GB, and > > two 50GB? Or is there a convention that all LUNs have to be > > a uniform > > size? > > > > Thanks! > > > > > > > > > > > > ___________________________ > > Chris Levis > > Applied Geographics, Inc. > > > > ------ > > You are subscribed as [EMAIL PROTECTED] > > Archives: http://www.swynk.com/sitesearch/search.asp > > To unsubscribe send a blank email to %%email.unsub%% > > > > ------ > You are subscribed as [EMAIL PROTECTED] > Archives: http://www.swynk.com/sitesearch/search.asp > To unsubscribe send a blank email to %%email.unsub%% > > ------ > You are subscribed as [EMAIL PROTECTED] > Archives: http://www.swynk.com/sitesearch/search.asp > To unsubscribe send a blank email to %%email.unsub%% > ------ You are subscribed as [EMAIL PROTECTED] Archives: http://www.swynk.com/sitesearch/search.asp To unsubscribe send a blank email to %%email.unsub%% ------ You are subscribed as [email protected] Archives: http://www.swynk.com/sitesearch/search.asp To unsubscribe send a blank email to [EMAIL PROTECTED]
