Re: Backup speed

Hello David,

David C. Partridge said on Thu, Dec 22, 2016 at 12:46:02PM +0000:
>I'm running a full backup now and the thing that's most noticeable is that
>the tape streamer isn't streaming even with the block size of 64K.

Maybe the buffer process in the middle is not giving enough to eat to your tape drive.

>I think this may be because the afioballs are relatively small files.  Is
>there a (relatively easy) way to change this.

Not at the moment. 
In the code the variable bkpinfo->optimal_set_size is the max value for an afio tar ball (by reading the code, I've not xritten that part).

And it's a fixed value:
bkpinfo->optimal_set_size = (IS_THIS_A_STREAMING_BACKUP(bkpinfo->backup_media_type) ? 16 : 16) * 1024L;
So 16 MB IIUC.

So whether we use a tape or not, it's the same atm. Maybe we need to change that no ?
I could add a flag to be able to change it e.g, and we could also keep it fixed as of now, but with a different default for tapes.

>I think that the large file part of the backup does manage to stream OK
>(from memory of my earlier testing).

There the -M parameter to change the size of what a Big file is, so you could try lowering that value (default 64MB).
Maybe creating more big files could help in your case, even if they are smaller.

Bruno.
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