Hey, toasters has been quiet lately, good to see some solid technical discussion on the agenda!

The 90% issue. I have only ever seen it degrade performance from an application/user perpective when the volume is holding database device files and being pounded. For flat files that don't change much, I wouldn't stress. If you have large snapshots for say, snapmirror, then I wouldn't go above 80% just in case.

Adding disk? Without sounding like a Netapp salesman, "the more the better". Never add one disk at a time. The rule is 3 minimum to provide better striping. Add one and you could see a significant performance hit as that disk thrashes away. NOW has more details on this.

From a pure technical design and efficiency perspective, I like Jim's suggestion.

If you can afford the disk, keep vol0 small and sacred, if you can't, then there is no reason why not to use the space.

The major caveat is the full volume backups and restores. I would do some careful calculations based on what I know about my backup solution. If your daily data changes are large and your backup windows small, you will have some backup problems. Even though double disk failure is extremely rare as Jim points out, if you have SLA's that specify a strict full restore window for that volume AND the volume DOES die ............. I hope your restores are fast.

Get your ducks lined up before you shoot with this one. I don't think backing out of the 1 volume will be as easy as going into it.

Aaron

-----Original Message----- From: Jim Harm [mailto:jharm@llnl.gov] Sent: Wednesday, 24 September 2003 3:03 AM To: pdunkin@lucent.com; toasters@mathworks.com Subject: Re: How many spares? Best way to use extras?

Let's start a warm thread.

My two cents is to: 1. build a ten disk raid from the 16 spares and set raid size to 9+1 2. migrate one of your eight disk raid/volumes to it as a qtree 3. destroy unused eight disk/volume 4. build another ten disk raid from left overs and previous volume 5. add this raid to the previous ten disk raid/volume to make big volume 6. migrate the next eight disk raid/volume to big volume as another qtree 7. continue to destroy old raids and migrate old to new volume as qtrees 8. when you are done you should have one big volume of four 10 disk raids and two hot spare disks.

I've had two disks fail on one system once in 4+ years and that was during the disk firmware upgrade that only temporarily failed them (had to power cycle). We have had several TB of data on NetApp filers at this sight over that period.

Use qtrees for all your exports to control space usage instead of building several volumes/raid strategies. It's simpler and more flexible. You can reapportion the space with little pain and no raid or volume reconfigures just by changing quotas.

Some may say "Whoa, you have to have a separate root volume!" I say "Baloney!. The only time I came close to losing a root volume was in the infancy of NetApp; we did have to reboot and use a different volume as root volume (I had copied the /etc to the non-root volume) because of a problem with the wack program, but even then we recovered the volume. Another concern might be that "We're afraid the root volume will get full!" which you can easily avoid by judicious and simple quotas. The only other thing I can think of is the time it takes to back up and restore by volume size.

At 11:56 AM -0400 9/23/03, Patricia A. Dunkin wrote:

Our F760 has 6 shelves and 42 36GB drives (running Data OnTAP 6.3.3 if that matters). Four volumes have been configured, with one RAID group in each volume; two have eight disks each, one has seven, and one that is mostly inactive archived stuff has four disks. That leaves fifteen (count 'em, 15) spares.

All the volumes except the archive are at or near 90% of capacity, a point at which I understand performance starts to plummet, and the storage needs of the users of the three active volumes continue to increase.

What is the optimal way to make use of the oversized pool of spares? Thoughts I've had:

• Create a new volume, put new projects there, and maybe move

some projects over from existing volumes, so everyone who needs it has room to grow.

• Add disks to the existing volumes gradually as needed, to keep

capacity under 90%. If I do this, is it better to add new disks one at a time or several at once? Is going over 90% really a problem, or is that just unfounded rumor?

Other suggestions are welcome. Also, how many spares would it be appropriate to keep as spares? I've been told that one per shelf would be enough, but some postings in the archives indicate that that may be on the generous side.

Thanks!

Patricia Dunkin Lucent Technologies pdunkin@lucent.com 600 Mountain Avenue 3C-306C Phone: 908-582-5843 Murray Hill, NJ 07974-0636 Fax: 908-582-3662 Pager: 888-371-8506 Mailto: 8883718506@skytel.net