Re: [pbs-devel] [PATCH proxmox-backup v2 0/7] improve catalog handling

Re: [pbs-devel] [PATCH proxmox-backup v2 0/7] improve catalog handling

[Dietmar Maurer]

> On 07/26/2021 10:37 AM Dominik Csapak <d.csapak@proxmox.com> wrote:
> 
>  
> On 7/26/21 10:26 AM, Dietmar Maurer wrote:
> > 
> >> On 07/22/2021 3:40 PM Dominik Csapak <d.csapak@proxmox.com> wrote:
> >>   
> >> this series combines my previous catalog related patch-series[0][1][2]
> >>
> >> changes the catalog interface to be more concise, optimizes catalog
> >> commit calls during restore, and implements a fast catalog for the
> >> gui which only contains the snapshot lists
> >>
> >> changes from v1:
> >> * only write snapshot list in new 'finish' method of the catalog
> >> * add 'finish' also to pool writer
> >> * replace pending offset counter with reducing the chunk_archive
> >>    interface of the catalog
> > 
> > Now, during tape backup, users do not see any progress on the GUI. This
> > can be particularly confusing on long running tape backups.
> > 
> > A simpler approach would be to only generate cache files for "finished" tapes (content
> > will never change), while using the original catalog for tapes still writable. This should
> > be much easier to implement?
> > 
> 
> yes it would be simpler, but this does not completely solve the issue of
> slow reads on large slow catalogs? (the last tape of the media-set can
> still be so big that the reads take too long?)

I thought the performance problem is on media-sets with many tapes. 
A single catalog should not cause a large delay?

Re: [pbs-devel] [PATCH proxmox-backup v2 0/7] improve catalog handling

[Dominik Csapak]

On 7/26/21 10:43 AM, Dietmar Maurer wrote:
> 
>> On 07/26/2021 10:37 AM Dominik Csapak <d.csapak@proxmox.com> wrote:
>>
>>   
>> On 7/26/21 10:26 AM, Dietmar Maurer wrote:
>>>
>>>> On 07/22/2021 3:40 PM Dominik Csapak <d.csapak@proxmox.com> wrote:
>>>>    
>>>> this series combines my previous catalog related patch-series[0][1][2]
>>>>
>>>> changes the catalog interface to be more concise, optimizes catalog
>>>> commit calls during restore, and implements a fast catalog for the
>>>> gui which only contains the snapshot lists
>>>>
>>>> changes from v1:
>>>> * only write snapshot list in new 'finish' method of the catalog
>>>> * add 'finish' also to pool writer
>>>> * replace pending offset counter with reducing the chunk_archive
>>>>     interface of the catalog
>>>
>>> Now, during tape backup, users do not see any progress on the GUI. This
>>> can be particularly confusing on long running tape backups.
>>>
>>> A simpler approach would be to only generate cache files for "finished" tapes (content
>>> will never change), while using the original catalog for tapes still writable. This should
>>> be much easier to implement?
>>>
>>
>> yes it would be simpler, but this does not completely solve the issue of
>> slow reads on large slow catalogs? (the last tape of the media-set can
>> still be so big that the reads take too long?)
> 
> I thought the performance problem is on media-sets with many tapes.
> A single catalog should not cause a large delay?
> 

many tapes makes the problem worse/more likely, but in general
if my disk is too slow to read a catalog in reasonable time, the
ux suffers. AFAIU a single catalog can be larger than 250MiB, which,
when on a storage that is slow to begin with and maybe under load,
can take quite some time to read completely.

e.g. 300MiB / 10MiB/s (slow spinner + big load) = 30s

not great ux when i have to wait more than half a minute to show the
content of my tape backup

in contrast, having a tape with 100000 snapshots with a 'fast catalog'

100000 * 50 bytes ~ 5 MiB should load in under a second

Re: [pbs-devel] [PATCH proxmox-backup v2 0/7] improve catalog handling

[Dominik Csapak]

On 7/26/21 10:26 AM, Dietmar Maurer wrote:
> 
>> On 07/22/2021 3:40 PM Dominik Csapak <d.csapak@proxmox.com> wrote:
>>   
>> this series combines my previous catalog related patch-series[0][1][2]
>>
>> changes the catalog interface to be more concise, optimizes catalog
>> commit calls during restore, and implements a fast catalog for the
>> gui which only contains the snapshot lists
>>
>> changes from v1:
>> * only write snapshot list in new 'finish' method of the catalog
>> * add 'finish' also to pool writer
>> * replace pending offset counter with reducing the chunk_archive
>>    interface of the catalog
> 
> Now, during tape backup, users do not see any progress on the GUI. This
> can be particularly confusing on long running tape backups.
> 
> A simpler approach would be to only generate cache files for "finished" tapes (content
> will never change), while using the original catalog for tapes still writable. This should
> be much easier to implement?
> 

yes it would be simpler, but this does not completely solve the issue of
slow reads on large slow catalogs? (the last tape of the media-set can
still be so big that the reads take too long?)

also, the 'progress' they do not see is only in the 'content' view.
the task log of the running tape backup still shows the normal progress.

what about my suggestion to indicate a running backup in the content 
view instead ? so the user knows this is still running.

also what if the tape is damaged later in the backup? then the user
saw that some things are backed up, but in reality the tape
is broken and nothing is properly backed up?

also the progress in the content view was incomplete anyway
since we only updated that once every 128GiB (that can be
many snapshots) or at the end of the tape/backup

so if we do not want to update the cache only at the end of the 
backup/tape, i'd rather suggest to regenerate the cache on
each pool_writer commit, so we can profit from it even on
non-finished tapes

Re: [pbs-devel] [PATCH proxmox-backup v2 0/7] improve catalog handling

[Dietmar Maurer]

> On 07/22/2021 3:40 PM Dominik Csapak <d.csapak@proxmox.com> wrote:
>  
> this series combines my previous catalog related patch-series[0][1][2]
> 
> changes the catalog interface to be more concise, optimizes catalog
> commit calls during restore, and implements a fast catalog for the
> gui which only contains the snapshot lists
> 
> changes from v1:
> * only write snapshot list in new 'finish' method of the catalog
> * add 'finish' also to pool writer
> * replace pending offset counter with reducing the chunk_archive
>   interface of the catalog

Now, during tape backup, users do not see any progress on the GUI. This 
can be particularly confusing on long running tape backups.

A simpler approach would be to only generate cache files for "finished" tapes (content 
will never change), while using the original catalog for tapes still writable. This should 
be much easier to implement?

[pbs-devel] [PATCH proxmox-backup v2 0/7] improve catalog handling

[Dominik Csapak]

this series combines my previous catalog related patch-series[0][1][2]

changes the catalog interface to be more concise, optimizes catalog
commit calls during restore, and implements a fast catalog for the
gui which only contains the snapshot lists

changes from v1:
* only write snapshot list in new 'finish' method of the catalog
* add 'finish' also to pool writer
* replace pending offset counter with reducing the chunk_archive
  interface of the catalog

0: https://lists.proxmox.com/pipermail/pbs-devel/2021-July/003711.html
1: https://lists.proxmox.com/pipermail/pbs-devel/2021-July/003715.html
2: https://lists.proxmox.com/pipermail/pbs-devel/2021-July/003714.html

Dominik Csapak (7):
  tape: media_catalog: improve chunk_archive interface
  tape: media_catalog: add fast_catalog beside normal catalog
  tape: pool_writer: finish the catalog when its done
  tape: media_catalog: add local type aliases to make code more clear
  api2: tape/backup: commit pool_writer even on error
  api2: tape/restore: finish temporary catalog at the end
  api2: tape: media: use MediaCatalog::snapshot_list for content listing

 src/api2/tape/backup.rs             | 117 +++++++++----------
 src/api2/tape/media.rs              |  44 ++++----
 src/api2/tape/restore.rs            |  11 +-
 src/tape/media_catalog.rs           | 167 +++++++++++++++++++++++++---
 src/tape/pool_writer/catalog_set.rs |   9 +-
 src/tape/pool_writer/mod.rs         |  15 ++-
 6 files changed, 250 insertions(+), 113 deletions(-)

-- 
2.30.2