On May 17, 2012, at 12:19 PM, Paynter, Richard wrote: > I have a customer who wants to set zfs_arc_max to 1G for a 16G system, and 2G > for a 32G system. Both of these are SAP and/or Oracle db servers. They > apparently want to maximize the amount of memory available for the > applications.
This is the best use case of the zfs_arc_max tunable. > > My question, now, is whether it would be advisable to do this, and – if not – > what the impact might be. For this use case, it is a good idea. The impact of not setting it occurs when you later want to start a memory-hogging program, the request for arc to shrink can take a little while to satisfy, and the memory-hog might not be designed to cope with retrying large memory allocation requests. > > The 32G system is an M3000; the 16G system is a V490. Both are running > Solaris 10 Update 8, patched to 147440-09. > > I have a feeling that setting zfs_arc_max this low is not a good idea, but > would like to get some corroborating information/references, if possible. This use case is why the zfs_arc_max tunable exists. -- richard -- ZFS Performance and Training richard.ell...@richardelling.com +1-760-896-4422
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