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On 03/25/2011 quotas have been enabled on cluster greentail. Because group quota numbers are weird, it is like counting duplicates or following links or looping, not sure, we have to rely on individual quotas. Just as well.

Here is what was put in place, and will mature over time. But first, it is important to understand:

• A quota is not disk space allocated for you, as in reserved. It is simply a threshold (soft/low) that can be adjusted, or not.
• Reason for quotas: to avoid /home from filling up by a runaway process, and constrain large users from growing beyond arbitrary thresholds.

The quotas fall into two tiers: the sliding tier and the custom tier.

• In the sliding tier, when you reach your soft limit, notify HPC admins and your quota will slide to the next strata (< 90/100G, < 225/250G, < 450/500G, < 700/750G). Once you reach the last strata, and you still need more disk space, you enter the custom tier.
• In the custom tier, we set a quota after agreeing on size and availability of disk space, plus 100G. Then you are on your own.

We urge all users to consider archiving data and files off the cluster disk array.

How to find my quota? You can find your quota levels and current usage as follows. Units are in kilobytes. So the blocks soft limit (quota) below is 90 GB, the hard limit (limit) is 100 GB.

• The hard block limit is the absolute maximum amount of disk space that a user can use. Once this limit is reached, no additional disk space can be used. Writes to disks will fail.
• The soft block limit defines the maximum amount of disk space that can be used. Unlike the hard limit, the soft limit can be exceeded for a certain amount of time. That time is known as the grace period.
• The grace period is globally set for 7 days.

[hmeij@greentail ~]$ quota -v hmeij

Disk quotas for user hmeij (uid 8216): 
     Filesystem  blocks   quota   limit   grace   files   quota   limit   grace
/dev/mapper/vghome-lvhome
                1227284  90000000 100000000            1020       0       0        

• Implementation
• add usrquota,grpquota options to fstab, remount
• log everybody out or reboot (quota error on boot, not initialized yet)
• quotaoff
• quotacheck -cvug /home (file system goes read only! 10TB of whcih 6TB used, took 3 hours)
• set default user quota and propagate to all users
• set custom quotas for other users
• wrap adduser
• quotaon
• group quota numbers do not add up !?

• Array
• 48 TB minus 4 global spares
• after formatting 36 TB available
• /home 10, /snapshots 10, /sanscratch 5 after that leaves 11 TB
• snapshots holds base plus deltas hence needs to be somewhere between 1-2x base
• so if we wanted to increase home, we could not use sanscratch (is anybody using it?)
• if we do not backup, then … questions for later

• Links
• Quota mini HOWTO
• Admin: Quotas
• useradd wrap and default quotas
• quotacheck invocation, file system goes read only

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