On 9/20/06, Yu Safin <[EMAIL PROTECTED]> wrote:
Given the results from the IBM benchmark and the comments in this paper, I am a bit confused as to when to use FCP and when to use ECKD. Assuming an EMC Symm. disk subsystem, zVM and SLES, wouldn't I want to keep my multipath simple by using ECKD and manage the I/O's via zVM using mini-Disks?
Aren't we all. Basically the paper says "it depends" but takes a few more pages for it. One hope would be that you have only a few virtual servers that have extreme disk I/O requirements (either in size or I/O bandwidth). For those servers you would accept the extra trouble to manage them. And for the rest you accept some latency in data access but get all the flexibility and other benefits of z/VM doing your data. And you will need to measure to understand which servers need that special treatment.
Most of my I/O's are solve either in cache under Linux or cache under zVM or cache in the I/O subsystem before I actually get to a device (mostly Oracle applications). I do hit heavy writes but normally off-hours when I don't care much.
When you do Linux in virtual machines that are fairly idle, you do not want to give them so much memory that they can cache all their data just-in-case, at least not as much as you would on discrete servers. Rob -- Rob van der Heij Velocity Software, Inc http://velocitysoftware.com/ ---------------------------------------------------------------------- For LINUX-390 subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390
