The first option is not good either because the moment you increase the size of the raid group and add only 1 drive, all the new writes are going to that one drive until it catches up in space utilization as the rest of the drives in that raid group. Performance will come to a screeching halt.
So NetApp definitely will let you do it but at the risk of really bad performance. The only way I would do this is to back up everything, blow the volume away, create the volume again with all the drives and then restore the data. NetApp typically suggest you add at least a few drives at a time. Sorry.
Derek
-----Original Message----- From: Stewart, John [mailto:johns@artesyncp.com] Sent: Thursday, June 03, 2004 2:44 PM To: 'toasters@mathworks.com' Cc: IT Technical Services Subject: Best practices for new RAID group
We've got an F740 with three shelves of 36GB disks (the 3rd recently added).
We've only got one volume, vol0, with 14 disks in it now (13 data and one parity). We use both CIFS and NFS. We have 7 spare disks (6 of which we'd like to eventually use for data, with one spare of course).
I just went to add one of the spare disks to vol0 (running low on space) and got the error:
vol add: starting a new RAID group; at least two disks are needed
So, as I (now) understand it, we've got to either:
- Override the 14 disk limit for a RAID group
or
- Add a new RAID group to the current volume
or
- Add a new volume
The 3rd choice is unattractive because we like the idea of One Huge Filesystem, that we can divvy up as needed into different qtrees.
The 2nd choice sounds like a Bad Idea in that according to this document, section 3.4: http://www.netapp.com/tech_library/3027.html, that the filer will try to distribute writes evenly between the old and new RAID group... if the new RAID group only contains two disks (we don't want to add more disk space than is needed now), this could be disatrous to performance
So is the 1st choice, increasing the size of the RAID group, a viable option? What is the downsize? Only increased risk of a double disk failure taking out the whole system? Is it possible to add a second parity disk to the same RAID group?
Am I missing something here? Any clue-by-fours quite welcome.
thanks
johnS