[OpenAFS] Balancing usecnts of RO volumes

[Jason Edgecombe]

On 12/17/2011 09:41 PM, Garance A Drosihn wrote:
> Hello.  A minor question here.
>
> I was curious if there was some way to encourage clients to load-
> balance their references across multiple RO volumes.  I have a
> volume which is fairly large (for us), and is often referenced
> about 10,000 times an hour.  I wanted to move that volume to new
> fileserver partitions.
>
> Before the move, the usage was pretty balanced between RO copies,
> for example:
>
>   VolumeID  Type Fsrvr/part UsedMB Usecnt  LastUpdate  CreateDate
>  ---------- ---- ---------- ------ ------ ----------- -----------
>   537373184   RW afsfs13/a    6040    281 11L26@22:08 04F07@15:34
>   537373185   RO afsfs13/a    6040 246409 11L23@13:45 11L23@13:45
>   537373185   RO afsfs15/a    6040 242495 11L23@13:45 11L23@13:45
>
> (the above is output from a script I wrote.  The only column I care
> about is the 'Usecnt' one).  Here are the numbers on a later date,
> just minutes before I made any changes:
>
>   VolumeID  Type Fsrvr/part UsedMB Usecnt  LastUpdate  CreateDate
>  ---------- ---- ---------- ------ ------ ----------- -----------
>   537373184   RW afsfs13/a    6041   6067 11L30@12:08 04F07@15:34
>   537373185   RO afsfs13/a    6041  30252 11L30@11:01 11L30@11:02
>   537373185   RO afsfs15/a    6041  27215 11L30@11:01 11L30@11:02
>
> I then created a new RO volume, and released it:
>
>   VolumeID  Type Fsrvr/part UsedMB Usecnt  LastUpdate  CreateDate
>  ---------- ---- ---------- ------ ------ ----------- -----------
>   537373184   RW afsfs13/a    6041   9719 11L30@13:34 04F07@15:34
>   537373185   RO afsfs13/a    6041   5258 11L30@13:18 11L30@13:23
>   537373185   RO afsfs15/a    6041   3675 11L30@13:18 11L30@13:23
>   537373185   RO afsfs12/b    6041      0 11L30@13:18 11L30@13:23
>
> I'm not sure it's important, but it happened that someone else had
> vos-released the volume maybe 5-10 minutes before I did, without
> me realizing they had until I had already done my vos-release.
>
> Maybe 10 minutes later, I vos-removed one of the older RO's:
>
>   VolumeID  Type Fsrvr/part UsedMB Usecnt  LastUpdate  CreateDate
>  ---------- ---- ---------- ------ ------ ----------- -----------
>   537373184   RW afsfs13/a    6041   9719 11L30@13:34 04F07@15:34
>   537373185   RO afsfs13/a    6041   7490 11L30@13:18 11L30@13:23
>   537373185   RO afsfs12/b    6041      8 11L30@13:18 11L30@13:23
>
> I don't mind that the access usecounts are out-of-balance at that
> point, but that was back on November 30th.  That volume is modified
> and vos-released at least two or three times per weekday.  And here
> we are on the 17th, and the RO volume on afsfs13/vicea is still
> referenced much more often than the new one on afsfs12/viceb:
>
>   VolumeID  Type Fsrvr/part UsedMB Usecnt  LastUpdate  CreateDate
>  ---------- ---- ---------- ------ ------ ----------- -----------
>   537373184   RW afsfs13/a    5619    494 11M17@21:11 04F07@15:34
>   537373185   RO afsfs13/a    5619  57495 11M17@18:36 11M17@18:37
>   537373185   RO afsfs12/b    5619    108 11M17@18:36 11M17@18:37
>
> It's probably true that this volume is referenced from a small
> number of client machines (web servers), and those machines are
> rarely rebooted.  But is there some way to encourage the clients
> to balance out the references?  The volume hasn't been very busy
> today, but I've seen other days where the RO on afsfs13/a has been
> referenced 500,000 times, and the one on afsfs12/b less than 2,000
> times.
>
> I do plan to move these specific volumes around some more over the
> winter break, so the state of this volume will be changing anyway.
> But it seemed like an interesting question.
>
Use "fs setserverprefs" on each client (web server) to set which servers 
that the clients prefer.

http://docs.openafs.org/Reference/1/fs_setserverprefs.html

There is a corresponding "fs getserverprefs"  commands to list the 
current server preferences.

Jason

http://docs.openafs.org/Reference/1/fs_setserverprefs.html