[aduitsis]

Very insightful comment on the data rate, if you can't feed the LTO properly, it may be stopping and starting all the time, which could have a detrimental effect to its mechanism. But this is probably easily fixed by spooling (using bacula terminology). You buffer like 100Gbytes, write them in one batch. Plus, some drives support variable speeds.

Also, in addition to SAS, a fibre channel card would also fit the bill, albeit probably a trifle more expensive. But if you go for low speeds (e.g. 8Gbps), those cards can be less than 100$.

[adrian_b]

Yes, that is how it should be done.

For example, I collect all the files that I send to backup in archive files whose size is approximately 50 GB, then I copy to the tape the 50 GB files.

Doing like this, the write speed to a LTO-7 drive is always constant at 300 MB per second, which is the maximum possible for that standard (which is much higher than what a HDD can sustain, so the 50 GB files must come from a fast SSD or from a RAM disk).

[at_a_remove]

I didn't know -- or perhaps remember -- that you had to match the feed against the speed, sort of like the way you had to be very careful about burning CD-Rs in the old days, but that makes perfect sense.

I have been fearfully realizing that I will soon need tape backup for my next project and this is helpful. Now I am wondering if a RAID 0 of multiple HDDs could provide the ~300 MB/s speed needed.

[adrian_b]

You do not have to match the speed, but you should.

Sending the data fast enough to the drive will reduce both the total time required for backup, when the drive is active, and it will also avoid starting and stopping a lot the drive during the transfer.

Both eliminating the start-stop cycles and reducing the total active time will increase the life of your tape drive.

On my server I have 128 GB of DRAM, which makes it extremely easy to ensure maximum speed without wearing a SSD.

When the backup starts, I create an 80-GB RAM disk, larger than the up to 60 GB archives in which I collect the files sent to backup.

With less memory one could either use smaller chunks or use a SSD instead of the RAM disk, but that seems wasteful.

Then the archive files are buffered in the RAM disk and written in one command, without pauses.