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LTO4 Compression Ratio
- Thread starter cabraun
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- Thread starter
- #2
Ohh one other question as well. Speed? I would be curious to know what people in the real world are seeing in the way of performance increase of LTO4 over technology such as LTO2. I believe LTO4 is supposed to be 3 times faster than LTO2.
Is that what people are seeing?
Is that what people are seeing?
LWComputingMVP
IS-IT--Management
IGNORE COMPRESSION. That's the easiest way to have problems with your backups, basing your buying decisions on the compressed capacity. The compression doesn't generally vary all that much from technology to technology. What does vary is the data you're backing up. The data YOU backup could be VASTLY different than the data I backup and the compression ratios in turn could be vastly different. In general, expect databases and text files to compress very well. Expect MPGs, JPGs, ZIPs, and other files to compress very poorly. In general, you can hope for 1.2-1.4 compression ratios - don't expect 2.0 compression ratios unless you're backing up a file you know contains a LOT of repetative data in it.
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- #4
I know that compression ratios will vary based upon what is being backed up. I can tell you that in our environment using LTO2 technology we, on average are seeing 2:1 compression and therefore are getting, on average, 400GB on a single LTO2 tape. Yes we do get some tapes with just over 200GB on it and I have seen as much as 900GB on a single LTO2 tape. But we are averaging 400GB on a tape.
So based upon what we currently se with LTO2, is it reasonable for me to assume I will be getting, on average 1.6TB on a single LTO4 tape? I know I will end up with some tapes getting just 800GB on them and I figure I will probably see 3TB or more on a single tape if the data written to it is that compressable.
Are those realistic assumptions on my part based upon my findings with our current LTO2 technology?
So based upon what we currently se with LTO2, is it reasonable for me to assume I will be getting, on average 1.6TB on a single LTO4 tape? I know I will end up with some tapes getting just 800GB on them and I figure I will probably see 3TB or more on a single tape if the data written to it is that compressable.
Are those realistic assumptions on my part based upon my findings with our current LTO2 technology?
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- #5
So I just thought I would update this post with what we are seeing since the install of our LTO4 drives.
Since migrating to the new library 2 weeks ago, I have filled 15 of my LTO4 tapes to capacity.
On average we have gotten 1.3TB on each tape.
The tape with the least data holds 1.07TB.
The tape with the most data holds 2.04TB.
I think of us as a fairly standard enterprise shop. About 110 Windows servers. Exchange, Oracle, SQL. Some custom apps. File servers, print servers etc.
Since migrating to the new library 2 weeks ago, I have filled 15 of my LTO4 tapes to capacity.
On average we have gotten 1.3TB on each tape.
The tape with the least data holds 1.07TB.
The tape with the most data holds 2.04TB.
I think of us as a fairly standard enterprise shop. About 110 Windows servers. Exchange, Oracle, SQL. Some custom apps. File servers, print servers etc.
LWComputingMVP
IS-IT--Management
My question is, which data are you getting those compression rates on? I would not be surprised to see that on Oracle and SQL databases (the 2.04TB). I would expect your File Servers are doing the 1.07 TB.
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- #7
I do not dedicate certain types of data to certain tapes, so it is safe to say that tape A one night might get Exchange and File server data while tape B gets Oracle and SQL data. The next night perhaps appendable tape A will get Oracle and Exchange while appendable tape B gets SQL and files. Then on the 3rd night perhaps appendable tape A will get Exchange and SQL while appendable tape B gets Oracle and files until both tapes are filled to capacity and results might be 1.2TB on tape A and 2.1TB on tape B.
darkoverlord2279
Technical User
Cabraun, What is the speed you get with your LTO4? I'm get 80 MB/sec (LTo3's write speed) when it's supposed to be 130 MB/sec.
Re. the speeds. LTO4's require the data to come off the servers pretty quick, and I suspect that there will be times when this just ain't going to happen.
One little trick, I'm sure you be aware of ...
Also, possibly dependant on the backup software ...
Try multiplexing several machines to one tape, trail and error, but try say 4, this way, hopefully the data flow will be quick enough from all 4 so that at some point, at least one of them is "ready to write", so if one has a slow moment, one of the others will take it's place.
Martin
One little trick, I'm sure you be aware of ...
Also, possibly dependant on the backup software ...
Try multiplexing several machines to one tape, trail and error, but try say 4, this way, hopefully the data flow will be quick enough from all 4 so that at some point, at least one of them is "ready to write", so if one has a slow moment, one of the others will take it's place.
Martin
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