12-18-2013 07:45 AM
We're running Data Protector 6.2 on a Windows Server 2008 box and one of the backup jobs is a filesystem backup that backs up a drive on a virtual (vSphere 5) Windows Server 2008 box. Currently the job is backing up around 2TB of data taking approximately 26 hours and is currently using 6 LTO3 tapes which doesn't seem right somehow. The backup hardware is an MSL 6000 with two LTO3 drives. The backup only uses one of them. I've checked the tape drive it is using and it has hardware compression enabled.
Where else can I look to try and reduce the number of tapes this job uses?
12-18-2013 09:04 AM
LTO3 tape capacity is 400GB (800GB compressed). Obviously, the compression that you'll achieve will depend upon the type of data that you're backing up. There will also be a bit of extra data on the tape other than pure data. Five tapes @ 400GB each would provide you with 2TB and I'm guessing that there's not much data on the sixth.
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12-19-2013 01:10 AM
Thanks for your reply.
I take it that this is expected behaviour then? I thought we would get more compression on the backups.
The data is predominately image files.
If I go into the tape properties and look at the data usage does this give an accurate indication of how much data is being stored?
12-19-2013 04:35 AM
well i would say for 2TB of data you would need about 5 Tapes. if it is more than 2TB it can go to 6 but as already have been told, it depends on the data you backup. in dp go to device and media -> media -> pools. then click on the media -> properties -> usage. there you should see how much data is on it if the tape is full.
is write compression enable in data protector?
device and media -> device -> in the properties of the device go to Drives tab and check if the tape address does end with an C. for example tape0:0:1:0C. If so, compression in DP is enabled.
If you have an HP Library or drive, you can use HP Library and Tape tools to enable/disable compression on the tape itself. you can also do some write testings to see if the compression is enabled.
But if you backup already compressed image files, you can not expect big compression with backup.
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12-23-2013 12:17 AM
There a lot of reasons possible. Is your topology fast enough to keep the drive writing? LTO 3 is 80MB/sec native assume 2:1 compression, you will have to feed it 160MB/sec. More realistic is about 1:4:1 which brings you to 114MB/sec, about a full Gigabit. Now of you deliver data too slow the drive will slow down and still keep in streaming but there might very well be 'empty spots' on your drive whenever data is not delivered for a second.
In addition about compression, assuming you do full disk-image backups, note that at least on Windows having for example a 1TB drive with 900GB free does not mean the raw image of the disk is mostly empty. If the disk had been filled up completely at one point in time, deleting files does not actually delete the data from disk. RAW imaging means all that 'non-existing' data is backed up as well. That might lead to unexpected compression results. Sure enough, if you make a RAW image backup of a 1TB disk which really has 900GB of zeros your compression will be awesome.