On 8/5/2020 2:16 AM, deloptes wrote:
Leslie Rhorer wrote:
DAR allows for not only incremental backups, but also incremental
deletions. ??I find it extremely useful, and allows for as much space
saving on the live system as one likes. ??I suggest you check it out.
someone should ask them to implement deduplication, because nowdays it is
impossible to do meaningful backups without.
In this context what, exactly, is de-duplication? I fail to see how
any meaningful interpretation of the term is salient to backups. To
compression, yes, to symbolic interpretation, surely, and to saving
space on a drive and reducing access times, you bet. To backups? I
don't really see it, unless you mean hard-link handling, which it does
most admirably. Soft links, of course, are fairly straightforward. DAR
does handle sparse files exceedingly well.
May I ask what is your active disk size
What do you mean by "active" disk size? In each of my main arrays
there are 8 spindles of 8 Terabytes each. Six spindles worth are
encoded with flat data and 2 spindles worth with parity. RAID 6 does
not assign any disks specifically for data or for parity as RAID 3 and
RAID 4 do. Instead, with both RAID 5 and RAID 6, parity is distributed
across every drive, and the data is also distributed across all the
drives, interleaved with the parity. All put together, the available
volume size is 46.9 Terabytes (43.6 Teribytes) after formatting. The
main server currently has 22 Terabytes of data on it. The backup server
is effectively full.
and how big is the disk size of the
backup?
The individual drives vary in size. Mostly they are 3 Terabytes, but
some are 2T and some are 4T. Future backups are going to be to 5T and
8T drives. It doesn't really matter. DAR does not care. For ease and
simplicity, I usually format each drive into a single file system and
direct DAR to use slices just under 100G. This results in no more than
100G of wasted space on any drive, and usually far less.
What kind of compression does it (DAR) support.
With my main system, it doesn't really matter, because the vast
majority of the data (more than 95%) is incompressible. In general,
gzip, bzip2, lzo, xz/lzma algorithms are directly supported by DAR, and
DAR supports both inclusion and exclusion parameters.
