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PACE quarterly maintenance – January ’16

This entry was posted by on Friday, 15 January, 2016 at

Greetings!

The PACE team is once again preparing for maintenance activities that will occur starting at 6:00am Tuesday, January 26 and continuing through Wednesday, January 27.  We have a couple of major items that hopefully will provide a much better PACE experience.

Transition to new scratch storage

Building on the new DDN hardware deployed in October, this item is the dominant activity in this maintenance period.  Our old Panasas scratch storage has now exceeded its warranty, so this is a “must do” activity.  Given then performance level of the Panasas and the volume of data it contains, we do not believe we will be able to migrate all data during this maintenance period.  So, we will optimize the migration to maximize the number of users migrated.  Using this approach, we believe we will be able to migrate more than 99% of the PACE user community.  After the maintenance window, we will work directly with those individuals who we are not able to migrate.  You will receive an email when your migration begins, and when it is complete.  (Delivered to your official GT email address, see previous post!)

After the maintenance period, the old Panasas scratch will still be available, but in read-only mode.  All users will have scratch space provisioned on the new GPFS scratch.  Files for users who are successfully migrated will not be deleted, but will be rendered inaccessible except to PACE staff.  This provides a safety net in the unlikely event that something goes wrong.

For the time being, we will preserve the 5TB soft quota and 7TB hard quota on the new GPFS scratch, as well as the 60 day maximum file age.  However, the timestamps of the files will get reset as they migrate, so the 60 day timer gets reset for all files.

The ~/scratch symlinks in your home directories will also be updated to point to the new locations, so please continue to use these paths to refer to your scratch files.  File names beginning with /panfs will no longer work once your migration is complete.

Scheduler update

Pending successful testing, we will also be rolling out a bug fix update to our Moab & Torque scheduler software and increase network connectivity for our most heavily used schedulers.  Among issues addressed in this release is a bug where we have seen erratic notifications about failures canceling jobs, incorrect groups being included in reports and some performance improvements.  Unlike previous scheduler upgrades, all previously submitted jobs will be retained.  No user action should be required as a result of this upgrade.

Server networking

We will be upgrading network connectivity on some of our servers to take advantage of network equipment upgraded in October.  No user action required.

GPFS tuning

We will adjust parameters on some GPFS clients to more appropriately utilize their Infiniband connections.  This only affects the old (6+ years) nodes with DDR connections.  We will also substitute NFS access for native GPFS access on machines that lack Infiniband connectivity or have otherwise been identified as poorly performing GPFS clients.  In particular, this will affect most login nodes.  The /gpfs path names on these machines will be preserved, so no user action is needed here either.

Filesystem migration – /nv/pk1

The /nv/pk1 filesystem for the Aryabhata cluster will be migrated to GPFS.

Read-Only /usr/local

The /usr/local filesystem will be exported read-only.  This is a security measure, and should not impact normal operations.

Diskless node transition

We will continue the transition away from diskless nodes that we started in October.  This mainly affects nodes in the 5-6 years old range.  Apart from more predictable performance of these nodes, this should also be a transparent change.

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