On Jul 16, 2013, at 2:41 AM, Shane Ambler wrote: > On 16/07/2013 14:41, aurfalien wrote: >> >> On Jul 15, 2013, at 9:23 PM, Warren Block wrote: >> >>> On Mon, 15 Jul 2013, aurfalien wrote: >>> >>>> ... thats the question :) >>>> >>>> At any rate, I'm building a rather large 100+TB NAS using ZFS. >>>> >>>> However for my OS, should I also ZFS or simply gmirror as I've a >>>> dedicated pair of 256GB SSD drives for it. I didn't ask for SSD >>>> sys drives, this system just came with em. >>>> >>>> This is more of a best practices q. >>> >>> ZFS has data integrity checking, gmirror has low RAM overhead. >>> gmirror is, at present, restricted to MBR partitioning due to >>> metadata conflicts with GPT, so 2TB is the maximum size. >>> >>> Best practices... depends on your use. gmirror for the system >>> leaves more RAM for ZFS. >> >> Perfect, thanks Warren. >> >> Just what I was looking for. > > I doubt that you would save any ram having the os on a non-zfs drive as > you will already be using zfs chances are that non-zfs drives would only > increase ram usage by adding a second cache. zfs uses it's own cache > system and isn't going to share it's cache with other system managed > drives. I'm not actually certain if the system cache still sits above > zfs cache or not, I think I read it bypasses the traditional drive cache. > > For zfs cache you can set the max usage by adjusting vfs.zfs.arc_max > that is a system wide setting and isn't going to increase if you have > two zpools. > > Tip: set the arc_max value - by default zfs will use all physical ram > for cache, set it to be sure you have enough ram left for any services > you want running. > > Have you considered using one or both SSD drives with zfs? They can be > added as cache or log devices to help performance. > See man zpool under Intent Log and Cache Devices.
This is a very interesting point. In terms if SSDs for cache, I was planning on using a pair of Samsung Pro 512GB SSDs for this purpose (which I haven't bought yet). But I tire of buying stuff, so I have a pair of 40GB Intel SSDs for use as sys disks and several Intel 160GB SSDs lying around that I can combine with the existing 256GB SSDs for a cache. Then use my 36x3TB for the beasty NAS. - aurf _______________________________________________ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "freebsd-questions-unsubscr...@freebsd.org"
