On Sun, Apr 4, 2010 at 4:52 PM, Robert Haas <robertmhaas@xxxxxxxxx> wrote: > On Fri, Apr 2, 2010 at 3:15 PM, Christiaan Willemsen > <cwillemsen@xxxxxxxxxxxxx> wrote: >> About a year ago we setup a machine with sixteen 15k disk spindles on >> Solaris using ZFS. Now that Oracle has taken Sun, and is closing up Solaris, >> we want to move away (we are more familiar with Linux anyway). >> >> So the plan is to move to Linux and put the data on a SAN using iSCSI (two >> or four network interfaces). This however leaves us with with 16 very nice >> disks dooing nothing. Sound like a wast of time. If we were to use Solaris, >> ZFS would have a solution: use it as L2ARC. But there is no Linux filesystem >> with those features (ZFS on fuse it not really an option). >> >> So I was thinking: Why not make a big fat array using 14 disks (raid 1, 10 >> or 5), and make this a big and fast swap disk. Latency will be lower than >> the SAN can provide, and throughput will also be better, and it will relief >> the SAN from a lot of read iops. >> >> So I could create a 1TB swap disk, and put it onto the OS next to the 64GB >> of memory. Then I can set Postgres to use more than the RAM size so it will >> start swapping. It would appear to postgres that the complete database will >> fit into memory. The question is: will this do any good? And if so: what >> will happen? > > I suspect it will result in lousy performance because neither PG nor > the OS will understand that some of that "memory" is actually disk. > But if you end up testing it post the results back here for > posterity... Err, the OS will understand it, but PG will not. ...Robert -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
