CBT Disk Usage (Plus some rubbish to make this over the 15 characters it "Must be"

client
1

I’ve been looking at the commercial CBT client, as I have a couple of internet clients where I think it would be particularly useful.
However, I have questions.

  1. How much disk activity does it incur in and of itself.

  2. If crash persistence is enabled on an SSD, how many writes does this subject it to? (Presumably many very small ones).

  3. What is the write amplification like in this case? As even the tiniest write involves the SSD writing an entire 4K block?

I wouldn’t worry on my own machines, but they’re not my machines, and they only have inexpensive consumer grade SSDs, I’d hate to recommend something that would cause those to wear prematurely.

Last question… any ballpark on when CBT might get implemented for file based backups? I’m not asking for a date, just an idea of weeks, months, or late next year / year after. I ask because I have some pretty big veracrypt containers, and quite a few .VHD and other VM disk image files I’ll be backing up in due course.

2

1, In non-crash persistent mode it only writes on startup, shutdown and when starting a backup
2. One sector per 512K touched on disk (worst case: double the write IOPS with random writes). Having active shadow copyies is worse for example.
3. Yeah

Just keep in in non-crash persistent mode (most people do that).

CBT for file backups is already implemented, just haven’t updated the web site yet. The server needs to be a new 2.1.x installation though (treehash hash mode).

3

Thanks for the response.
I may be making a couple of licence purchases in the near-ish future, not necessarily associated with the email this account uses…
I’ll probably be recommending purchase of a cheap UPS and thus obviating crash-persistent mode, given brownouts are relatively common compared to BSODs and that will enable me to enable some advantageous caching in addition.

The only BSODs I’ve seen in the last two years have been backup software related, one due to pssnap.sys in the case of old Macrium Reflect installs, and tcpip.sys with UrBackup, which on one client crashes networking and blue screens if I attempt any other remedial action besides a full reboot unless I restrict the speed to 50Mbpss on that client’s 100Mbps NIC,