Re: [zfs-discuss] upgrade zfs stripe

2010-04-20 Thread Albert Frenz
ok thanks for the fast info. that sounds really awesome. i am glad i tried out 
zfs, so i no longer have to worry about this issues and the fact that i can 
upgrad forth and back between stripe and mirror is amazing. money was short, so 
only 2 disks had been put in and since the data is not that worthy i was aware 
of non-redundancy. though after knowing that feature i will surely add a disk 
for that in the next time. thanks again.

adrian
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Re: [zfs-discuss] upgrade zfs stripe

2010-04-20 Thread Edward Ned Harvey
 From: Bob Friesenhahn [mailto:bfrie...@simple.dallas.tx.us]
 
 On Mon, 19 Apr 2010, Edward Ned Harvey wrote:
 
  Just be aware that if *any* of your devices fail, all is lost.
 (Because
  you've said it's configured as a nonredundant stripe.)
 
 The good news is that it is easy to convert any single-disk vdev into
 a mirror vdev.  It is also easy to convert a mirror vdev into a
 single-disk vdev.  This means that you can upgrade your simple
 stripe into a stripe of mirrors.

A really good point.

Yes, you can take a 2-disk stripe volume, and make a 4-disk stripe of
mirrors volume of the same size.

No, you cannot take a 2-disk volume, and make it a 3-disk raidz volume.
Unless you're willing to destroy and restore all your data.

Also, since the question was can I expand my volume just by adding more
disks this is worth mention too:  Whatever type of volume you have, be it a
stripe, a mirror, a stripe of mirrors, a raidz set, or whatever ... You can
always expand the volume by just adding disks to it.  But if you're adding
non-redundant disks, you're not fully redundant anymore.  If you add a
non-redundant disk to some pool that had redundancy, and your new disk dies,
then your pool is lost.

If you have a raidz volume, of n disks, you cannot simply add 1 disk, and
have a raidz volume of n+1 disks.

I don't know if I'm just adding to confusion here.  Sorry if it's not more
clear.

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Re: [zfs-discuss] upgrade zfs stripe

2010-04-19 Thread Edward Ned Harvey
 From: zfs-discuss-boun...@opensolaris.org [mailto:zfs-discuss-
 boun...@opensolaris.org] On Behalf Of Albert Frenz
 
 since i am really new to zfs, i got 2 important questions for starting.
 i got a nas up and running zfs in stripe mode with 2x 1,5tb hdd. my
 question for future proof would be, if i could add just another drive
 to the pool and zfs can integrate it flawlessly? and second if this hdd
 could also be another size than 1,5tb? so could i put in 2tb also and
 integrate it?

Absolutely no problem.

Just be aware that if *any* of your devices fail, all is lost.  (Because
you've said it's configured as a nonredundant stripe.)

Also, one of the best features of ZFS is automatic checksumming.  I love
that demonstration where they create a raid set, shutdown, insert the disks
into some other system, and start writing random bytes to random sectors ...
Put the disks back into the first system and bring it all up.  No data
errors, because they were detected and corrected.

Unfortunately, in a nonredundant configuration, you can only detect errors.
Not correct them.

So the arguments in favor of adding some redundancy are pretty compelling
for all but the most worthless data.  In your case, you would only need to
add one more disk ... 3x 1.5T disks in a raidz set ... total 3T usable, and
1 disk redundancy.

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Re: [zfs-discuss] upgrade zfs stripe

2010-04-19 Thread Bob Friesenhahn

On Mon, 19 Apr 2010, Edward Ned Harvey wrote:


Just be aware that if *any* of your devices fail, all is lost.  (Because
you've said it's configured as a nonredundant stripe.)


The good news is that it is easy to convert any single-disk vdev into 
a mirror vdev.  It is also easy to convert a mirror vdev into a 
single-disk vdev.  This means that you can upgrade your simple 
stripe into a stripe of mirrors.


Bob
--
Bob Friesenhahn
bfrie...@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,http://www.GraphicsMagick.org/
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