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Re: [zfs-discuss] Size discrepancy (beyond expected amount?)

Subject: Re: [zfs-discuss] Size discrepancy beyond expected amount?
From: Harry Putnam
Date: Thu, 19 Mar 2009 21:00:22 -0500
Bob Friesenhahn <bfriesen@xxxxxxxxxxxxxxxxxxx> writes:

> On Thu, 19 Mar 2009, Harry Putnam wrote:
>> I've created a zpool in raidz1 configuration with:
>>
>>  zpool create  zbk raidz1  c3d0 c4d0 c4d1
>
> This is not a very useful configuration.  With this number of disks,
> it is best to use two of them to build a mirror, and save the other
> disk for something else (e.g. to build a mirrored root pool). Mirrors
> perform better, are more fault tolerant, and are easier to administer.

Ok, I was going by comments on a site called Simons' blog that tells
you how to set things up with zfs.  Of course it is just one guys
opinion. 

Let me just say a couple of words about my intended usage.

I'm building a home NAS server for my home lan using opensolaris and
zfs.

I will be backing up 4 Windows XP boxes, 2 of which are used primarily
for processing video.  And eventully I'd be storing finished video
projects too.  Often these projects run to 50gb or so.  But I don't do
so many.  Maybe 9-12 in a yr.

So I'd want to put ghosted images of each machine OS (several apiece)
and running backups (incremental) that would stretch back a few weeks.
And the projects mentioned above.  As well as what is becoming quite a
large photo collection.

Also 2 linux boxes will getting backed up there.

I thought the kind of redundancy offered by raidz1 would be enough for
my needs and would allow me to get a little more storage room out of
my disks than mirrored setup.

I suspect as well, that the access times in raidz1 or mirrored would
be vastly higher than what the low end consumer grade NASs that are
availabe offer.

I did try one out.. a WD Worldbook (about $200 US) that advertises
gigabit access but in use cannot even come close to what a 10/100
connect can handle.

So raidz1 would probably be adequate for me... I wouldn't be putting
it to the test like a commercial operation might.

You mentioned admistration was a bigger problem with raidz1, can you
be more specific there?... I have really know idea what to expect in
that regard with either technique.

> With five disks, raidz1 becomes useful.

The three 500gb I have now are all one brand and model number and IDE ata.
If I were to expand to 5, those 2 would need to be sata or else I'd
also need to add a PCI IDE controller.

With that in mind would it be problematic to make up the 5 by adding 2
sata 500gb to the mix?

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