Saturday, October 24, 2009
Point in time copies, are they backups?
The simple answer is no, the more complex answer is it depends.
Point in time copies (snapshots) can drastically increase your time to recovery. And can be incredibly useful for data restoration due to an application/operating system/ file system/ user problem.
That being said, really the idea of a true backup is to handle DR and the failure of systems, disks and other problems. Being that your data and copies reside in the same hardware/location it does not protect you against such failures.
Now the reason above I stated is "it depends" is because some vendors are offering the replication of existing point in time copies to a remote system. So the idea is that when it resides on the same system it is not fully useful as a backup media but once it gets transfered/archived and if that archive container the sum total of the original data as well (So a mirror or replication) it can act as a full backup.
Current Problems
There is some possibilities here, If you are simply looking for a point in time to be able to restore to for DR for the short term you can fulfill this with a large archive of remote point in time copies (replicas) but with current vendors these technologies fall flat in two area's
1) Long term storage
A lot of vendors are trying to make improvements in this area but still fall short. While it may be feasible to store weeks or even months worth of daily snapshots is doable with some of todays vendors really keeping a lot of these around for years is non feasible. This storage space is also relativity expensive per GB compared tape and other media. At best it can be used as a "Mid Teir" place to store info to reduce your "race to daylight"
2) Archival, cataloging
No solution that I am aware of (and if you know any different please share!) really handles the cataloging on a file level that is available to some other server side tools. What happens when you have a user that asks "I deleted a very important document from 2 months ago, I don't remember its name exactly but it was financial something or other and was an excel spreadsheet" or "I have not looked at my important financial document in a year but someone changed it in the last year, I want the one that was modified in 2008"
With E discovery tools available to some backup solutions this is easy to do I just search for *financial*.xls? but with block level point in time copies this is not as easy.
Some vendors are making strides (specially if they also do file level shares) and are going in the right direction but are not there yet.
Long term storage
A nice trend I am seeing in industry is the ability to ship point in time copies off to alternative media, this is a great idea. Quite a few vendors are making an effort to be able to do things like use standard NDMP to be able to export the data directly from the SAN to something like a data domain or a VTL or directly to tape. This makes long term storage more feasible and economical.
My take on it
Point in time copies are a great way to prevent against many different types of non storage layer problems, and replicas can even help with that. But in the end without cataloging the usefulness and ability to do file level recovery and E-discovery is non existent. It may be perfectly fine for your industry but in some that is a challenge.
Point in time copies (snapshots) can drastically increase your time to recovery. And can be incredibly useful for data restoration due to an application/operating system/ file system/ user problem.
That being said, really the idea of a true backup is to handle DR and the failure of systems, disks and other problems. Being that your data and copies reside in the same hardware/location it does not protect you against such failures.
Now the reason above I stated is "it depends" is because some vendors are offering the replication of existing point in time copies to a remote system. So the idea is that when it resides on the same system it is not fully useful as a backup media but once it gets transfered/archived and if that archive container the sum total of the original data as well (So a mirror or replication) it can act as a full backup.
Current Problems
There is some possibilities here, If you are simply looking for a point in time to be able to restore to for DR for the short term you can fulfill this with a large archive of remote point in time copies (replicas) but with current vendors these technologies fall flat in two area's
1) Long term storage
A lot of vendors are trying to make improvements in this area but still fall short. While it may be feasible to store weeks or even months worth of daily snapshots is doable with some of todays vendors really keeping a lot of these around for years is non feasible. This storage space is also relativity expensive per GB compared tape and other media. At best it can be used as a "Mid Teir" place to store info to reduce your "race to daylight"
2) Archival, cataloging
No solution that I am aware of (and if you know any different please share!) really handles the cataloging on a file level that is available to some other server side tools. What happens when you have a user that asks "I deleted a very important document from 2 months ago, I don't remember its name exactly but it was financial something or other and was an excel spreadsheet" or "I have not looked at my important financial document in a year but someone changed it in the last year, I want the one that was modified in 2008"
With E discovery tools available to some backup solutions this is easy to do I just search for *financial*.xls? but with block level point in time copies this is not as easy.
Some vendors are making strides (specially if they also do file level shares) and are going in the right direction but are not there yet.
Long term storage
A nice trend I am seeing in industry is the ability to ship point in time copies off to alternative media, this is a great idea. Quite a few vendors are making an effort to be able to do things like use standard NDMP to be able to export the data directly from the SAN to something like a data domain or a VTL or directly to tape. This makes long term storage more feasible and economical.
My take on it
Point in time copies are a great way to prevent against many different types of non storage layer problems, and replicas can even help with that. But in the end without cataloging the usefulness and ability to do file level recovery and E-discovery is non existent. It may be perfectly fine for your industry but in some that is a challenge.
Labels: Backups, Point in time, SAN, Storage
# posted by Slackerhobo : 2:48 PM
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