I'm building out a FreeNAS based server that will primarily be used to serve up iSCSI disks to Xen virtual machines and dedicated servers. My current data need is for 8TB of space, growing at about 2TB per year. I have a Supermicro X6DHE-XB 3U enclosure with 4G of RAM, 16 SATA hot-swap bays that I will be using. It comes with 2x8 port 3Ware RAID cards, but I'm planning on just using the ZFS capabilities instead of the hardware RAID. My initial drive set will be 8x2TB HITACHI Deskstar 7K3000 HDS723020BLA642 drives.
I have 2 questions
- I will want to add additional drives to this server in the future and have them added to the storage pool. Ideally, I'd like to do this live without having to reboot or take the system off line. Are there any limitations or advantages to a ZFS mirror setup vs a RAID-Z setup for expanding the storage pool? With the hot-swap SATA ports, can I add a disk and have it show up in the FreeNAS GUI as available?
- If the performance penalty is less than 5% or so, I'd prefer to go with a RAID-Z2 setup so my initial volume size would be 12TB instead of 8TB with the mirrored config. This server will be pretty busy (serving up around 60 iSCSI targets), and unfortunately I have no way of testing it with a production load, besides putting it into production. I'd appreciate any real-world performance experience with RAID-Z serving large numbers of iSCSI targets.