Snapshot - what is it good for?

[TvrdyJ]

Hello,

in our backups, lot of them is failing on the famous snapshot error. So I would like to ask what is it good for? And what is the advantage of this?

I found general descriptions like that it is "photo" of the disk. The state of the data in current time.
I found lots of info about how to set up it.

But I still dont undersatnt - what is the advantage of this? Whn it is used? I mean - if I will disable snapshots - will it affect anythink? How it will affect recovery options?

Thank you very much

EDIT:
To be more precise... what will happen if I will ged rid of these lines in OPT file:
INCLUDE.FS C: FILELEVELTYPE=SNAPSHOT
INCLUDE.IMAGE "C:" IMAGETYPE=SNAPSHOT SNAPSHOTFSIDLERETRIES=50 SNAPSHOTFSIDLEWAIT=2S,25MS

And disable the snapshot providers:
SNAPSHOTPROVIDERFS NONE
SNAPSHOTPROVIDERIMAGE NONE

WIll the backups be drastically affected?

 

[witchdoctor]

Depends what is snapshotted.
Generaly snapshot mechanisms allow backup of files being currently open.
On Windows this is the only way to backup systemdir.
Sometimes specific applications need to be backed up, but they cannot be shut down, and there is no TDP, so... snapshot comes in, and lets You backup these applications.
So If You are not taking such backups (wich I belive is quite untrue), disable the snapshots nad get rid of LVSA.

 

[TvrdyJ]

So the snapshots are NECESSARY to backup system drive?
Because - I try to disable it... or at least I believe I did.. this is changed prt of the opt:

SNAPSHOTPROVIDERFS NONE
SNAPSHOTPROVIDERIMAGE NONE
* INCLUDE.FS "C:" FILELEVELTYPE=SNAPSHOT
* INCLUDE.IMAGE "C:" IMAGETYPE=SNAPSHOT SNAPSHOTFSIDLERETRIES=50 SNAPSHOTFSIDLEWAIT=2S,25MS

And I try the manual bakup with this result.

tsm> backup
Incremental backup of volume '\\hostname\c$'
Incremental backup of volume '\\hostname\d$'
Incremental backup of volume 'SYSTEMSTATE'
Successful incremental backup of '\\hostname\c$'
Successful incremental backup of 'Automated System Recovery'
Successful incremental backup of '\\hostname\d$'
Successful incremental backup of 'hostname\SystemState\NULL\System State\SystemState'

Total number of objects inspected: 36,455
Total number of objects backed up: 156
Total number of objects updated: 0
Total number of objects rebound: 0
Total number of objects deleted: 0
Total number of objects expired: 1
Total number of objects failed: 0
Total number of subfile objects: 0
Total number of bytes transferred: 126.92 MB
Data transfer time: 1.61 sec
Network data transfer rate: 80,476.61 KB/sec
Aggregate data transfer rate: 331.15 KB/sec
Objects compressed by: 69%
Subfile objects reduced by: 0%
Elapsed processing time: 00:06:32
tsm>


The previsous scheduled backups failed with
ANS1349E An error occurred during Logical Volume Snapshot Agent snapshot processing.
(No addidional error in the error log)
This result seems little bit like the improvement...

So was the system dir properly backuped or not? Is there any risk for me to leave it like that?

I have these snapshot errors on about 10 servers. It really gets on my nerve. But Im already running out of imagination how to fix them. I tried:
1) Deleting as much files as possible (hoping that less data and files will have lesses chance to fail)
2) Playing with SNAPSHOTFSIDLERETRIES=50 SNAPSHOTFSIDLEWAIT=2S,25MS (even to extremes)
3) changing INCLUDE.FS "C:" FILELEVELTYPE=SNAPSHOT to dynamic.

EDIT:
It tested it also on the other server (this time unfortunatelly W2k with the latest 5.3.6.0 tsm client version) - so I just commented that two "includ.fs/image" lines.
Result - Just one not important file skipped. And few warnings about
ANS1377W The client was unable to obtain a snapshot of '\\hostname\h$'. The operation will continue without snapshot support.
But followed with the:
Successful incremental backup of '\\hostname\h$'

Any risk for the data in this case?

 

[witchdoctor]

1)Snapshot is necessary when backing up open files (hence open file support).
Since files under windows sysdir are usually held open by windows....
2) If You are using LVSA there is no need to backup images of system drive.
Simple incremental backup will do the job.(just remember to exlude pagefile, recycler, prefetch and so on, and do not exlude $KB***** dirs, for future BMR)
3) Do not mistake SystemState backup with sysdir backup. What is in system state is needed, but does not contain full windows backup needed for BMR.

4) If You insist on taking image backup of system drive, use VSS as a SNAPSHOTPROVIDERIMAGE.

6) There are lots of threads on forums on troubleshooting LVSA. In my case it works well. Sometimes reinstalling LVSA, then client can fix the issues.
7) If possible - test the backups. Then You'll know what went wrong with the backup, before You'll actually face the the disaster ;-)

EDIT:

Add SNAPSHOTCACHELOCATION and SNAPSHOTCACHESIZE (in most of the cases, cache size is to small so increasing it might help - it is percentile value of volume being snapshotted)

 

[TvrdyJ]

1+3) Ok... but I I got the successful backup message about system drive and no files skipped - than sys dir was also backuped correctly right?

2+4) To be honest, these lines
INCLUDE.FS "C:" FILELEVELTYPE=SNAPSHOT
INCLUDE.IMAGE "C:" IMAGETYPE=SNAPSHOT SNAPSHOTFSIDLERETRIES=50 SNAPSHOTFSIDLEWAIT=2S,25MS
are there still as a remains from 5.3.x.x version. Im still not so confortable with these snapshot settings, so I was afraid to delete them.

So if Im not the 5.5 client and Im using
SNAPSHOTPROVIDERFS LVSA
SNAPSHOTPROVIDERIMAGE LVSA
these both include fs/image lines can be deleted without any risk? (sound good to me )

I dont insist on have them there... if recovery will works fine even without it. I was just afraid to delete it... that the reason of this thread - to find out what it is good for, and if I can safely disable the part that is causing the snapshot error.

6) I read lots of them. hleped me on some servers. But I have still some stubborn bastart servers, wit hthese failures...

ad EDIT) - I have these lines there (I jsut did not copyed them) - and Im sure there is lot of free space for these snapshots.

 

[TvrdyJ]

BTW:
DOMain.image C:

Is it neccessary? Is it needed (in 5.5 with LVSA)? Is it the one you mentioned I dont need?

Sorry for these stupid questions. We cotovered the backups fully setted up. The enviroment is that i can not make experimetns (DR) as I want... So some part are still mystery but I can not affort some big error in my attemps to fix it...

 

[witchdoctor]

DOM.Image C: for 5.5 with LVSA can be safely replaced by DOMain C:
About 5.3 version, I have no experience with it. Try doing test restores with files backed up with 5.3 with these lines commented.
Upgrade to 5.5.x.x client (don't remember wich one is the newest). Usually it solves alot of problems.

 

[TvrdyJ]

Well. I have already Doman All-local.
So I will remove the DOmain.image C

Upgrade to 5.5.x.x solved most of our snapshot issues. Unfortunately some os is sitll W2k (latest version is 5.3.6.0 as far as I know). And somewhere its making trouble even after upgrade.
maybe there is more of these unnecessary opt lines that just remains after the upgrade... ?

Iny ideas? (the node and IP are censored. Some customer are sensitive about security and I really dont want them to ask why they can google it )

COMMmethod TCPip
NODENAME **********
TCPSERVERADDRESS **********
TCPPort 1504
TCPNodelay Yes
TCPWindowsize 63
TCPBuffsize 32
TXNBytelimit 25600
LANGuage ENU
SCHEDLOGName c:\adsm\baclient\dsmsched.log
ERRORLOGName c:\adsm\baclient\dsmerror.log
SCHEDLOGRetention 14 D
ERRORLOGRetention 14 D
SCHEDMODe polling
PASSWORDAccess generate
RESOURceutilization 5
COMPRESSIon YES
COMPRESSAlways No
DISKBuffsize 256
MANAGEDServices schedule
QUIET
SNAPSHOTCACHESIZE 15
DIRMc MCDIR
* POSTSchedulecmd c:\adsm\baclient\postschedule.cmd
* PRESchedulecmd c:\adsm\baclient\preschedule.cmd
DOMain ALL-LOCAL
* DOMain.image C:
DATEformat 5
TIMEformat 1
SUbdir Yes


* INCLUDE.FS C: FILELEVELTYPE=SNAPSHOT
* INCLUDE.IMAGE "C:" IMAGETYPE=SNAPSHOT SNAPSHOTFSIDLERETRIES=50 SNAPSHOTFSIDLEWAIT=2S,25MS


Exclude.dir "*:\System Volume Information"
Exclude.dir "*:\...\Temporary Internet Files"
Exclude.dir *:\Recycled
Exclude.dir *:\Recycler
Exclude.dir *:\WINDOWS\temp
Exclude.dir *:\temp
Exclude.dir *:\tmp
Exclude "*:\Documents and Settings\...\INDEX.DAT"
Exclude "*:\Documents and Settings\...\ntuser.*"
Exclude "*:\Documents and Settings\...\usrclass.*"
Exclude "*:\Documents and Settings\...\Temporary Internet F*\...\*"
Exclude *:\...\adsm\...\*dsm*.log
Exclude *:\...\IBM\Director\...\*.log

SNAPSHOTPROVIDERFS LVSA
SNAPSHOTPROVIDERIMAGE LVSA

But there is still one think I dont understad. Backup with this opt (w2k3, 5.5.1.0 client) hav ethis error:
ANS1380W The snapshot operation failed. The filesystem write activity prevented the Logical Volume Snapshot Agent from satisfying the SNAPSHOTFSIDLEWait and SNA PSHOTFSIDLERetries options.

Is there any reason for it? As I see in the opt - the domain.image is removed. So why it is trying to take snapshot?

 

[rscherrer47]

Snapshots are great for servers that are going to be retired...ie data retention of several years due to HIPA requirements or a financial institution. (year end copy).

This type of "backups" would relieve some database storage as well , as a side benefit.

Regards,

R