[lustre-discuss] Expanding a zfsonlinux OST pool

Faaland, Olaf P. faaland1 at llnl.gov
Mon Nov 23 13:35:11 PST 2015

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?


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


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).


[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?


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