Snapshots

Snapshots are a implementation of copy on write that allows for a file system to quickly take a point in time copy of the file system and provide access to the data through a .snapshot directory.

We provide Snapshots on our ONStor filers to certain file systems.

Snapshot Policy

Our core file systems in the department are on a 4 hour snapshot cycle. Snapshots are taken at,

12am

4am

8am

12pm

4pm

8pm

We retain up to 8 hourly snapshots, 2 daily snapshots and 1 weekly snapshot.

These are available on the following [OpenLAB] file systems,

NFS

• /nfshomes
• /fs/www
• /fs/www-users
• /fs/ftp

CIFS

• \\umiacsfs02.umiacs.umd.edu\nfshomes
• \\umaics-webftp.umiacs.umd.edu\www-umiacs
• \\umaics-webftp.umiacs.umd.edu\www-users
• \\umaics-webftp.umiacs.umd.edu\ftp-umiacs

Please see [SnapshotFileSystems] for a list of our file systems that have snapshots in the department.

Snapshot Restoring

If you find that you have mistakenly deleted a file and it was created/written to before the last snapshot[1]. You can restore the file by going to the directory where the file was and changing into the .snapshot directory and then using a normal copy operation to copy it back to the directory where you would like it. Please note that the .snapshot directory is hidden and may not appear when you do a directory listing.

[1] - If a file was created or modified after the last snapshot then you can potentially lose up to 4 hours of work in a worse case scenerio. Please make sure you save your work throughout the day.

Example:

Changing to my quotes directory.

[derek@novelty quotes]$ pwd
/nfshomes/derek/work/quotes

I see that i have a quote called redhat_sole_source_2007.doc.

[derek@novelty quotes]$ ls
dlt_pdf_quote2007.pdf  Quote_300086759.html         redhat_solesource.pdf
dlt_pdf_quote.pdf      Quote_353511914.html         soleSource2007.pdf
dlt_quote.pdf          Quote_367512608.html         soleSource.pdf
dy1014.xls             Quote_367884529.html         UMD_008.xls
Quote_250530976.html   redhat_sole_source_2007.doc

[derek@novelty quotes]$ ls -la redhat_sole_source_2007.doc 
-rw-r--r-- 1 derek derek 39936 Jan 23  2007 redhat_sole_source_2007.doc

I will remove it from the current file system.

[derek@novelty quotes]$ rm redhat_sole_source_2007.doc 

As you can see it no longer is there.

[derek@novelty quotes]$ ls 
dlt_pdf_quote2007.pdf  Quote_250530976.html  Quote_367884529.html   UMD_008.xls
dlt_pdf_quote.pdf      Quote_300086759.html  redhat_solesource.pdf
dlt_quote.pdf          Quote_353511914.html  soleSource2007.pdf
dy1014.xls             Quote_367512608.html  soleSource.pdf

I am going to go into the last hourly snapshot hourly.0

[derek@novelty quotes]$ cd .snapshot/hourly.0

As you can see the quote is still here.

[derek@novelty hourly.0]$ ls
dlt_pdf_quote2007.pdf  Quote_300086759.html         redhat_solesource.pdf
dlt_pdf_quote.pdf      Quote_353511914.html         soleSource2007.pdf
dlt_quote.pdf          Quote_367512608.html         soleSource.pdf
dy1014.xls             Quote_367884529.html         UMD_008.xls
Quote_250530976.html   redhat_sole_source_2007.doc

I copy it back to the original directory.

[derek@novelty hourly.0]$ cp redhat_sole_source_2007.doc /nfshomes/derek/work/quotes/

Change back to the original directory.

[derek@novelty hourly.0]$ cd /nfshomes/derek/work/quotes/

And it is back.

[derek@novelty quotes]$ ls
dlt_pdf_quote2007.pdf  Quote_300086759.html         redhat_solesource.pdf
dlt_pdf_quote.pdf      Quote_353511914.html         soleSource2007.pdf
dlt_quote.pdf          Quote_367512608.html         soleSource.pdf
dy1014.xls             Quote_367884529.html         UMD_008.xls
Quote_250530976.html   redhat_sole_source_2007.doc