gm_sjo wrote: > 2008/9/6 Ben Rockwood wrote: > >> Does that help you out? Want me to elaborate on this more? >> > > Hi Ben. Yes, that's great - thanks. > > On the hardware side, i'm seeing people still steer towards having > hardware array controllers when using zfs.. I was hoping to use raidz2 > with a bunch of sata disks hanging off of a.n.other generic > controller. Do you have any recommendations on storage controllers? Am > I likely to run into any problems if I use a proper Intel motherboard > with onboard sata controller? >
ZFS was designed to make the most of cheap and unreliable hardware. In fact, in many cases your better off using a bunch of SATA/SAS drives directly rather than using hardware raid controllers... this is because when you give ZFS access to the raw drives it stores multiple copies of the data, which can be used to recover from checksum errors, and such, as well as better utilize on-drive caches. Unless you have a HW RAID Card with a 256MB Write Back Cache, don't bother at all. Just as an example... what is a Thumper? An X4100 server with 6 (or is it 8, I forget) SATA controllers and 48 500GB Hitatchi (typically) 7,200RPM disks with 8MB caches. Nothing really spectacular, frankly, except that they crammed it all into 4U. There is nothing particularly high-end or special aside from the way its packaged together (which itself is brilliant). Whats important about Thumper is that its only ZFS that makes it exciting. Putting Linux on one would be a nightmare to manage; the same goes for Solaris without ZFS. Only ZFS can make that baby sing and not cause you to loose your mind. > I'd be very interested too to see any performance stats from software > raid configs (of any kind really, but preferably using iscsi) - to get > an idea of what kind of cpu hit we're talking about. I know that's > very broad and fairly useless, but some info is better than none. > Checksumming incurs CPU overhead, but you'll rarely really notice it (<2%). Compression can jump that up quite a bit, but I've never really seen a case that caught my attention. If you're using a CPU 1Ghz or faster you'll not have a problem. On smaller micro-laps such as an EEE PC or something you might get more conscious of these things. The one recommendation I'll make that may not immediately be self-evident is to put as much memory in the box as possible. The more memory for caching (ZFS ARC) the better. I'd argue that you'd do better to save yourself a couple hundred bucks on a good HW RAID controller and instead sink the cash into extra memory. benr. _______________________________________________ storage-discuss mailing list [email protected] http://mail.opensolaris.org/mailman/listinfo/storage-discuss
