NFS zfs serveur (hardware question)

Damien Fleuriot ml at
Thu Jun 23 01:31:15 UTC 2011

On 22 Jun 2011, at 15:41, Michel Le Cocq <miconof80.list at> wrote:

> Hi all, I'm planning to change my data NFS server. For 60 clients.
> I wanted to serv NFS for data over NFS and also for diskless host
> (
> Here is the harware I chose :
> a little proc : 1.6 Ghz Xeon 4 coeurs (mono)
>  : It's seems that on a such server the proc is just Waiting for
>    IO... !?
> a lot of Ram : 24 Go 
> speedy disk : Sas 15K 
>  : to limit IO Wait
> What do you think of a such conf ?
> --
> M
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You'll need to be much more accurate to get helpful answers.

What usable storage size do you need ? 2T ? 5T ? 15T ?
What kind of performance do you need ?
How many slots do you have for hard drives ?
Do you want 2.5 or 3.5 size factor disks ?
What kin of data security do you want ? (is the data critical ?)
Can you afford downtime / incidents during which the data will be unavailable ?
Is this a dumb file server or are you going to use NFS for example for your database or web servers ?
What is your budget for this ?
Are you going to use compression ? (no, you're not, trust me)
Are you going to use snapshots ?

As a rule of thumb and for a serious server, I would recommend 1 SSD as dedicated cache and 2 SSD for a mirrored ZIL (you don't want to lose this data).
However I think ppl posted about running intro trouble when using both ZIL and cache disks, so I suggest you only get the ZIL.

An example of a viable setup would be:
9x 500gb 15k disks for data
2x 32gb SSD disks for ZIL

Then, create 3 zraid pools with 3 disks each (try to put each disk within the pool on a different controller).
Now, create a new zraid pool using your 3 pools.

Effectively, you get:

datapool (zraid1, 2TB usable)
   zraid1 (1TB usable)
      disk A1
      disk B1
      disk C1
   zraid1 (1TB usable)
      disk A2
      disk B2
      disk C2
   zraid1 (1TB usable)
      disk A3
      disk B3
      disk C3
   ZFS Intent Log
      SSD A4
      SSD B4

You will lose your main ZFS pool if you lose:
- more than 1 of your full ZFS pools
- your ZIL (need confirmation on that)

Now, the odds of that happening are rather low...

If you're lucky, Jeremy Chadwick will have thoughts on the matter.

For the most efficient help, re-read my questions above, these are important considerations.

There are a lot of different pool setups available, and both have their pros and cons.
Tell us what you're looking for, and I'm sure we can hatch a good solution.

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