Optimal ZFS setup

[pudlos]

Hi I have built FreeNAS server based on MSI board with Phenom 2.6Ghz Quad core 6Gb RAM, 2 Gigabit NIC's 3 1Tb drives in ZFS volume + 2 40GB sata hdd's currently setup as cache drives. What would be optimal setup for this config? Does it make any sense to use this drives for cache? Should I use one of the 40GB for cache and one for logs or don't use them at all? Freenas is loaded on 8Gb usb stick. Thank you in advance Martin

 

[Joshua Parker Ruehlig]

40gb is way more then you'd need for logs, ive read that you only need as much as your system can write suequentualy for 5 seconds. But it may help as you wont have to touch the data disk to use a hdd as a zil. I personally would try all the different config out (if you don't have data on them yet). Just try different ones out and test. also know that if your zil harddrive dies you lose EVERYTHING in your zpool. this is until freenas gets zpool v19 or higher I believe.

 

[xbmcg]

I would not add regular sata hdd as cache drives - it does not make sense. It would be an option, if you have a sata3-ssd or so. Otherwise you will probably slow down your system. The RAM is your fastest cache and if you do not overload the speed of your hd's in the pool, the cache does nothing - since there is no "overflow" of incomming bytes greater than outgoing bytes AND the RAM Cache is full.

 

[pudlos]

How can I remove this 2 sata drives from cache without need of reinstalling freenas from scratch? What the CLI command for that?

 

[louisk]

If you want to use the cache feature, buy an SSD. You should also think about the type of data you access frequently and figure out the total size of that data, you will need to get an SSD big enough for that (no, I'm not talking about your entire data set, just the frequently used data).

If you have VM performance issues, you could also use a mirrored SSD for ZIL (log). If you're not doing anything with VM, I would ignore the ZIL.

 

[pudlos]

Thank you for all the info. so from all you guys are saying it doesn't make too much sense to use these 2 old 40gb sata drives. How can I safely remove them from freenas? I don't want to go thru whole reinstalling/setting up everything again. Is there any way to do it? Thanks in advance
Martin

 

[louisk]

ZFS doesn't care if you remove the cache on the fly. You can't remove the ZIL until v28 comes out.