ZFS Server Configuration

S

Sylgeist

I have acquired a few servers for basic infrastructure services at work (mail/ftp/proxy/jails/etc) and would like suggestions on the best ZFS layout for the hardware. I've been searching through the docs, but I'm not clear on what's best.

Hardware:
  • 8-way Nehalem
  • 2x1TB enterprise SATA
  • 2x160GB Intel SSDs
  • 48GB RAM

These are the options I see:
  1. Install OS on UFS SSDs and create ZFS on SATA with SSD cache partitions
  2. Install OS on SATA and use mirrored cache on SSD
  3. Install OS on ZFS SSD pool and create separate SATA pool

I'm leaning toward #2, but I don't want to waste the SSD capacity if there is a better way to architect it. These machines will eventually have maybe 30-40 jails of various services with nothing individually I/O heavy.

Thanks!
 
There are a few basic things to understand here:

1. ZIL is best done on SSD. ZIL should be mirrored (at least), as if it dies, the array dies. ZIL usually remains small, 2GB of ZIL would probably do fine, but the smallest SSDs are 8GB, I think..

2. L2 cache (not memory) is also best done by SSD. Don't bother mirroring cache, if it fails, it's simply expired.

3. Read: http://www.solarisinternals.com/wiki/index.php/ZFS_Best_Practices_Guide I'm sure you're sick of being linked here, but it really is a good read.
 
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