VDISK requests are synchrounous - if they are handled by pages already in VM's storage somewhere. Rob did some tests, ran swap to vdisk at something like 40,000/second. is that fast enough? I don't see any value in having multiple vdisks for swap. The real question is what happens when a request to vdisk is made - that actually takes a page fault, does linux get redispatched? The answer will be the same if there is one vdisk or many. So no perceived benefit of having multiple vdisks.
>Date: Tue, 1 Apr 2003 14:17:52 -0500 >From: "Post, Mark K" <[EMAIL PROTECTED]> >Dennis, > >If your Linux/390 guests were doing a _lot_ of swapping, I can >see how something like this would let Linux schedule swap I/O to >the multiple devices more "in parallel." Since I have no feel >for how fast VM turns those requests around for a vdisk, it may >or may not buy you anything. This would be something I'd want >Barton to take a look at and see what he thinks. I don't think >theorizing about it will get us very far. Interesting idea, >though. > > >Mark Post > >-----Original Message----- >From: Dennis Wicks [mailto:[EMAIL PROTECTED] > >I don't think I have seen this particular aspect of V-DISK swap >space discussed here before. > >Is there any thing in either VM or linux that would make the use >of multiple V-DISK swap spaces better or worse than a single one? > >I don't mean just one versus two but more on the order of >ten 100 meg. swap areas versus one 1 gig. swap area. Or even >something like ten 50 meg. areas vs. one 500 meg. area. > >The reaon for the question is that it is easier to set these things >when first defining the guest than it is to come back later and >retrofit them. > >Thanks for any insights! > >Dennis "If you can't measure it, I'm Just NOT interested!"(tm) /************************************************************/ Barton Robinson - CBW Internet: [EMAIL PROTECTED] Velocity Software, Inc Mailing Address: 196-D Castro Street P.O. Box 390640 Mountain View, CA 94041 Mountain View, CA 94039-0640 VM Performance Hotline: 650-964-8867 Fax: 650-964-9012 Web Page: WWW.VELOCITY-SOFTWARE.COM /************************************************************/
