# ZFS and different disks



## Migelo (Dec 17, 2012)

Hi!

Currently I have HTPC configured like this;
HW:

AMD Athlon II x2 260
GIGABYTE GA-M68M-SP2
4GB DDR2 800MHz RAM
1xWD 500GB 7.2k
3xWD Green 2TB in RAID5

Now, I'm upgrading. I'll be running FreeBSD with  Buying 3 new disks , but which one?

For convenience's sake, let's say, I have these on my disposal:
http://www.hoh.de/hardware/festplat...14-2000gb-3-5-sata-6gb/s-7200rpm-64mb?c=30090

http://www.hoh.de/hardware/festplat...5k3000-2000gb-sata-6gb/s-5400rpm-32mb?c=30090

http://www.hoh.de/hardware/festplat...d-caviar-green-2000gb-sata-i6gb/s-3.5?c=30090

Which one? The specifications say that Seagate has only 2400 power on hours / year specified, can't find data for other disks though. I only know that the WD Green are hated by a lot of people and software for their aggressive head parking and lacking-TLER support. 
How does ZFS deal with combining different disks?


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## Sebulon (Dec 18, 2012)

@Migelo

ZFS doesnÂ´t care what disks you have, at all

So you can mix-match whatever you want. TLER is not required, but still a nice feature to have. What is does is that when ZFS recieves a request about IO that should be read/written, if the underlying drive is damaged and canÂ´t accomodate that, the drive can come back early to say, "I couldnÂ´t". Without that, ZFS has to wait for another instance to reply, e.g. controller/driver to reply in a similar manner, and if they donÂ´t, ZFS continues to wait, and wait, and wait...

/Sebulon


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## Sfynx (Dec 19, 2012)

AFAIK the only thing that is really required is that the disks and disk controllers do not lie about when the data has been really persisted (e.g. reached the platters, or a non-volatile battery backed cache memory), because ZFS depend on that for data consistency. So it helps to keep the logic between ZFS and the drives as simple as possible, I tend to only use disks on 'dumb' HBA's.

But that's not even ZFS specific.. if the storage system lies about cache flushes you're basically walking the edge of a cliff with any file system


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## Migelo (Dec 19, 2012)

Ok, thanks!

So which controller would you suggest? Does the IBM ServeRaid M1015 really work amazing with FreeBSD?


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## Migelo (Dec 19, 2012)

Actually, this is a completely different topic, so please answer my controller-related question here: http://forums.freebsd.org/showthread.php?p=201439


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