Going to try this out.
Stephen
On 11/05/2012 02:40 PM, Josh Fisher wrote:
>
> On 11/5/2012 4:28 PM, Stephen Thompson wrote:
>> On 11/05/2012 01:17 PM, Josh Fisher wrote:
>>> On 11/5/2012 11:03 AM, Stephen Thompson wrote:
>>>> On 11/5/12 7:59 AM, John Drescher wrote:
>>>>>> I've had the following problem for ages (meaning multiple major
>>>>>> revisions of bacula) and I've seen this come up from time to time on the
>>>>>> mailing list, but I've never actually seen a resolution (please point me
>>>>>> to one if it's been found).
>>>>>>
>>>>>>
>>>>>> background:
>>>>>>
>>>>>> I run monthly Fulls and nightly Incrementals. I have a 2 drive
>>>>>> autochanger dedicated to my Incrementals. I launch something like ~150
>>>>>> Incremental jobs each night. I am configured for 8 concurrent jobs on
>>>>>> the Storage Daemon.
>>>>>>
>>>>>>
>>>>>> PROBLEM:
>>>>>>
>>>>>> The first job(s) grab one of the 2 devices available in the changer
>>>>>> (which is set to AutoSelect) and either load a tape, or use a tape from
>>>>>> the previous evening. All tapes in the changer are in the same
>>>>>> Incremenal-Pool.
>>>>>>
>>>>>> The second jobs(s) grab the other of the 2 devices available in the
>>>>>> changer, but want to use the same tape that's just been mounted (or put
>>>>>> into use) on the jobs that got launched first. They will often literal
>>>>>> wait the entire evening until 100's of jobs run through on only one
>>>>>> device, until that tape is freed up, at which point it is unmounted from
>>>>>> the first device and moved to the second.
>>>>>>
>>>>>> Note, the behaviour seems to be to round-robin my 8 concurrency limit
>>>>>> between the 2 available drives, which mean 4 jobs will run, and 4 jobs
>>>>>> will block on waiting for the wanted Volume. When the original 4 jobs
>>>>>> are completed (not at the same time) additional jobs are launched that
>>>>>> keep that wanted Volume in use.
>>>>>>
>>>>>>
>>>>>> LOG:
>>>>>>
>>>>>> 03-Nov 22:00 DIRECTOR JobId 267433: Start Backup JobId 267433, Job=JOB.
>>>>>> 2012-11-03_22.00.00_0403-Nov 22:00 DIRECTOR JobId 267433: Using Device
>>>>>> "L100-Drive-0"03-Nov 22:00 DIRECTOR JobId 267433: Sending Accurate
>>>>>> information.
>>>>>> 03-Nov 22:00 sd_L100_ JobId 267433: 3307 Issuing autochanger "unload
>>>>>> slot 82, drive 0" command.
>>>>>> 03-Nov 22:06 lawson-sd_L100_ JobId 267433: Warning: Volume "IM0108"
>>>>>> wanted on "L100-Drive-0" (/dev/L100-Drive-0) is in use by device
>>>>>> "L100-Drive-1" (/dev/L100-Drive-1)
>>>>>> 03-Nov 22:09 sd_L100_ JobId 267433: Warning: Volume "IM0108" wanted on
>>>>>> "L100-Drive-0" (/dev/L100-Drive-0) is in use by device "L100-Drive-1"
>>>>>> (/dev/L100-Drive-1)
>>>>>> 03-Nov 22:09 sd_L100_ JobId 267433: Warning: mount.c:217 Open device
>>>>>> "L100-Drive-0" (/dev/L100-Drive-0) Volume "IM0108" failed: ERR=dev.c:513
>>>>>> Unable to open device "L100-Drive-0" (/dev/L100-Drive-0): ERR=No medium
>>>>>> found
>>>>>> .
>>>>>> .
>>>>>> .
>>>>>>
>>>>>>
>>>>>> CONFIGS (partial and seem pretty straight-forward):
>>>>>>
>>>>>> Schedule {
>>>>>> Name = "DefaultSchedule"
>>>>>> Run = Level=Incremental sat-thu at
>>>>>> 22:00
>>>>>> Run = Level=Differential fri at
>>>>>> 22:00
>>>>>> }
>>>>>>
>>>>>> JobDefs {
>>>>>> Name = "DefaultJob"
>>>>>> Type = Backup
>>>>>> Level = Full
>>>>>> Schedule = "DefaultSchedule"
>>>>>> Incremental Backup Pool = Incremental-Pool
>>>>>> Differential Backup Pool = Incremental-Pool
>>>>>> }
>>>>>>
>>>>>> Pool {
>>>>>> Name = Incremental-Pool
>>>>>> Pool Type = Backup
>>>>>> Storage = L100-changer
>>>>>> }
>>>>>>
>>>>>> Storage {
>>>>>> Name = L100-changer
>>>>>> Device = L100-changer
>>>>>> Media Type = LTO-3
>>>>>> Autochanger = yes
>>>>>> Maximum Concurrent Jobs = 8
>>>>>> }
>>>>>>
>>>>>> Autochanger {
>>>>>> Name = L100-changer
>>>>>> Device = L100-Drive-0
>>>>>> Device = L100-Drive-1
>>>>>> Changer Device = /dev/L100-changer
>>>>>> }
>>>>>>
>>>>>> Device {
>>>>>> Name = L100-Drive-0
>>>>>> Drive Index = 0
>>>>>> Media Type = LTO-3
>>>>>> Archive Device = /dev/L100-Drive-0
>>>>>> AutomaticMount = yes;
>>>>>> AlwaysOpen = yes;
>>>>>> RemovableMedia = yes;
>>>>>> RandomAccess = no;
>>>>>> AutoChanger = yes;
>>>>>> AutoSelect = yes;
>>>>>> }
>>>>>>
>>>>>> Device {
>>>>>> Name = L100-Drive-1
>>>>>> Drive Index = 0
>>>>>> Media Type = LTO-3
>>>>>> Archive Device = /dev/L100-Drive-1
>>>>>> AutomaticMount = yes;
>>>>>> AlwaysOpen = yes;
>>>>>> RemovableMedia = yes;
>>>>>> RandomAccess = no;
>>>>>> AutoChanger = yes;
>>>>>> AutoSelect = yes;
>>>>>> }
>>>>>>
>>>>> I do not have a good solution but I know by default bacula does not
>>>>> want to load the same pool into more than 1 storage device at the same
>>>>> time.
>>>>>
>>>>> John
>>>>>
>>>> I think it's something in the automated logic. Because if I launch jobs
>>>> by hand (same pool across 2 tapes devices in same autochanger)
>>>> everything works fine. I think it has more to do with the Scheduler
>>>> assigning the same same Volume to all jobs and then not wanting to
>>>> change that choice if that Volume is in use.
>>> When both jobs start at the same time and same priority, they see the
>>> same exact "next available volume" for the pool, and so both select the
>>> same volume. When they select different drives, it is a problem, since
>>> the volume can only be in one drive.
>>>
>>> When you start the jobs manually, I assume you are starting them at
>>> different times. This works, because the first job is up and running
>>> with the volume loaded before the second job begins its selection
>>> process. One way to handle this issue is to have a different Schedule
>>> for each job and start the jobs at different times with one second
>>> spacing. Jobs will still run concurrently, they just won't start up
>>> concurrently.
>>>
>> I suspected something like that, but would ask out loud "if bacula runs
>> into a contention like that and there are other available volumes in the
>> requested pool, why doesn't it decide to use another volume instead of
>> blocking?"
>
> See the Prefer Mounted Volume directive docs at
> http://www.bacula.org/5.2.x-manuals/en/main/main/Configuring_Director.html#SECTION0022150000000000000000
>
> This is a way to sort of deal with the issue, but is not ideal. I would
> prefer that the volume selection logic have an option to NEVER select a
> volume that is already loaded in another drive, or a volume that has
> been selected by another job unless the other job is assigned the same
> drive. This might indeed cause more tapes to be needed in a pool and be
> less efficient in terms of tape usage, but it would eliminate most of
> the problems encountered with concurrent jobs writing to the same pool.
>
>>
>> It's also disappointing, because we've already pulled virtually all of
>> our scheduling outside of bacula into scripts because the logic seldom
>> works out for us. This may be another case of that. I'm surprised this
>> isn't a more common concern. What could be more run-of-the-mill than
>> having a nightly incremental pool within an autochanger with multiple
>> drives?
>>
>> thanks!
>> Stephen
>>
>>
>>>> If I do a status on the Director for instance and see the jobs for the
>>>> next day lined up in Scheduled jobs, they all have the same Volume listed.
>>>>
>>>> thanks,
>>>> Stephen
>>>
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>>
>
>
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--
Stephen Thompson Berkeley Seismological Laboratory
stephen AT seismo.berkeley DOT edu 215 McCone Hall # 4760
404.538.7077 (phone) University of California, Berkeley
510.643.5811 (fax) Berkeley, CA 94720-4760
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