Problems on enabling snapshots after reboot,.

Problems on enabling snapshots after reboot,.

[Borut Rozman]

Hi everyone,

I have a machine where I run snapshots of the FS every 12 hours, and
keep a week lot of those snapshots. After a crash or a clean restart,
filesystem with snapshots does not get enabled and I have to wait
several hours for lvm snapshots to get back online which of course is
stressful. Last time I had to wait for 8 hours for all the snapshots to
get enabled and then I had to remove all the snapshots so my FS would
come up normally. I was wondering if this is a know issue or how can I
avoid this.

PS: FS is about 200TB in size and snapshots 5TB in size but they might
be even empty.

Borut

Re: Problems on enabling snapshots after reboot,.

[Zdenek Kabelac]

Dne 25. 10. 23 v 14:55 Borut Rozman napsal(a):
> Hi everyone,
> 
> I have a machine where I run snapshots of the FS every 12 hours, and
> keep a week lot of those snapshots. After a crash or a clean restart,
> filesystem with snapshots does not get enabled and I have to wait
> several hours for lvm snapshots to get back online which of course is
> stressful. Last time I had to wait for 8 hours for all the snapshots to
> get enabled and then I had to remove all the snapshots so my FS would
> come up normally. I was wondering if this is a know issue or how can I
> avoid this.
> 
> PS: FS is about 200TB in size and snapshots 5TB in size but they might
> be even empty.
> 

Hi

Unfortunately you are misusing the original *thick* snapshot purpose.
It's been designed to be a short living small sized object.
If your snapshot gets into the GiB range - it gets very very inefficient.

You should check the thin-pool and its snapshot capabilities - where your 
operation should be mostly instant then. And there is not a problem of 
amplified write when you take a multiple snapshot of the same volume and you 
can even take snapshot of a snapshot.

With 5TiB old thick snapshot there is simply a zero chance to fly.


Regards

Zdenek