[lustre-discuss] Expanding a zfsonlinux OST pool

Bob Ball ball at umich.edu
Mon Dec 7 08:09:44 PST 2015

Found this URL that outlines the procedure, and specifically mentions 
some details in regard to zfsonlinux.


On 11/23/2015 4:35 PM, Faaland, Olaf P. wrote:
> Hello Bob,
> We did something similar - our MDS's used zpools based on spinning 
> disks in JBODs and we switched to SSDs without bringing the filesystem 
> down, using ZFS to replicate data.  It worked great for us.
> How are your pools organized (ie what does zpool status show)? There 
> might be options that are more or less risky, or take more or less 
> time, depending on how zfs is using the disks.
> Also, how often are disks failing and how long does a replacement take 
> to resilver, with your current disks?
> -Olaf
> ------------------------------------------------------------------------
> *From:* Bob Ball [ball at umich.edu]
> *Sent:* Monday, November 23, 2015 12:22 PM
> *To:* Faaland, Olaf P.; Morrone, Chris
> *Cc:* Bob Ball
> *Subject:* Expanding a zfsonlinux OST pool
> Hi,
> We have some zfsonlinux pools in use with Lustre 2.7 that use some 
> older disks, and we are rapidly running out of spares for those.  What 
> we would _like_ to do, if possible, is replace all of those 750GB 
> disks in an OST, one at a time with re-silver between, with 1TB disks, 
> then expand the OST when the last is complete to utilize the larger 
> space and the more reliable disks.
> Is this going to work?  One of us here found the following:
>     According to the Oracle docs, a pool can autoexpand if you set it to
>     do so.  I think the default must be off because the one I checked is
>     off (but that does indicate support of the feature in the linux
>     release also).
>     http://docs.oracle.com/cd/E19253-01/819-5461/githb/index.html
>     [root at umdist02 ~]# zpool get autoexpand ost-006
>     ost-006  autoexpand  off     default
> We are using zfsonlinux version  Can we follow the procedures outlined in the oracle doc using zfsonlinux?
> I guess my initial question assumed the expansion would not happen until the last disk is added and re-silvered, but the document indicates this is not really necessary?
> Thanks,
> bob

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