Networker

Re: [Networker] Quick question on File System Devices for staging

2003-01-28 11:02:16
Subject: Re: [Networker] Quick question on File System Devices for staging
From: Joel Fisher <jfisher AT WFUBMC DOT EDU>
To: NETWORKER AT LISTMAIL.TEMPLE DOT EDU
Date: Tue, 28 Jan 2003 11:02:07 -0500
Sorry for the delay in response.

Thanks for taking the time to respond in such detail!!

I'll try to post my results once I've got staging into production.

Joel

-----Original Message-----
From: Jon Hickmott [mailto:jonny AT uwo DOT ca] 
Sent: Friday, November 15, 2002 9:04 AM
To: Legato NetWorker discussion; Joel Fisher
Subject: Re: [Networker] Quick question on File System Devices for
staging

I just finished testing staging and I did find some qotchas with this
configuration. In my test I had 3 areas and I set the default capacity
of each
area to be a third of the available disk space. Without setting the
default
capacity or
setting it to the size of the disk area caused some other issues so I
recommend
using the one third approach.

  1. The high and low water marks go by the available disk space and do
not the
     follow the space left in one of the FS devices. Therefore, even if
a FS
     device is over the high-water mark, a check file system will not
write
     savesets off to tape unless the available disk space is over the
high-water
     mark.
  2. Problem 1 lead to FS devices becoming 100% full and legato marking
the
     associated volume as (R)ead only. Legato will not set the volume to
     appendable once space becomes available. You must do this manually
by
     unmounting and changing the mode on the volume.
  3. When a check file system does run and the disk space is over the
high-water
     mark I could not get the low-water mark to work. All 3 area were
cleaned up
     completely. If you plan to leave savesets on disk for as long as
possible
     this can be an issue. My testing was with small disk areas over
short
     periods of time which may have something to do with the results.
  4. If you run out of available disk space during a backup and all 3 FS
devices
     are marked read only a check file system will clean the areas up
leaving
     the savesets that are currently being backed up. Once you set the
volumes
     to appendable the backup will complete BUT if the backup picks the
same FS
     device to finish writing a saveset it will OVERWRITE the saveset on
disk
     starting from the beginning of file. When you go to write this
saveset to
     tape it will give you errors that part of the saveset is lost. This
marks
     the saveset as bad and you lose the backup. You must now manually
correct
     this situation to get the disk space back. If you run into this
problem I
     suggest you add a tape to the staging pool and complete the backup
to tape.
     You can later change one of the FS devices to be in a clone pool
then use
     nsrclone to write the savesets on the tape back to disk. A stage
all
     savesets operation will then put them in their correct home.
Another option
     is to add another FS device if you have available disk space
somewhere
     else.

It is possible but if you are running on small disk area that
periodically run
out of space then you must be very careful.

FYI,
Jon

Joel Fisher wrote:

> Hey All,
>
> I would like to get around the odd limitation of not being able to
stage
> savesets to tape while the File System device has an incoming saveset
> stream.  Is there any reason not to have multiple directories setup as
> FS devices under one physical device?
>
> For Example:
>
> /dev/dsk/c3t0d0s2 is mounted on /fsdevices
> 3 directories call:
> /fsdevices/fd00
> /fsdevices/fd01
> /fsdevices/fd02
>
> FS devices setup pointing to the above 3 directories.
>
> Would this allow me to start staging savesets on FS device fd00 and
fd01
> even if data is still being written to fd02?
>
> Any known gotchas in this configuration?
>
> Thanks,
>
> Joel
>

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