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 PROTECTED]
