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#1 2021-07-28 10:51:02

d4t1983
Member
Registered: 2017-10-16
Posts: 11

XSIBackup-DC is it possible to --check on a remote over SSH replica?

Hi,

So I was replicating just happily to a remote Linux server over SSH then I received an error during backup. As such I want to run the --check option to ensure my replica is good but it always seems to error suggesting the path I have is incorrect.

Should --check work over SSH? If so can someone give me an example of how to run it correctly?

Thanks in advance!

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#2 2021-07-28 10:58:57

admin
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Registered: 2017-04-21
Posts: 1,821

Re: XSIBackup-DC is it possible to --check on a remote over SSH replica?

Can you share the output?, otherwise we can just especulate.
--check command is local, run from the remote Linux server.

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#3 2021-07-28 11:50:26

d4t1983
Member
Registered: 2017-10-16
Posts: 11

Re: XSIBackup-DC is it possible to --check on a remote over SSH replica?

Sure here you go:

root@dr0:/data/cbt_replicas# xsibackup --check /data/cbt_replicas/testvm/ --verbosity=10

-------------------------------------------------------------------------------------------------------------
SIGTERM (11) condition was trapped: check logs for more details
-------------------------------------------------------------------------------------------------------------
Cleaning up...
-------------------------------------------------------------------------------------------------------------

Nothing appears to be logged except in the kernel log I see the following (for example):

Jul 28 12:48:43 dr0 kernel: [443932.765980] xsibackup[41606] vsyscall attempted with vsyscall=none ip:ffffffffff600400 cs:33 sp:7ffd462c5fe8 ax:ffffffffff600400 si:73f691 di:0

This is on Debian 10.10... Does that help?

Last edited by d4t1983 (2021-07-28 11:50:35)

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#4 2021-07-28 12:01:59

d4t1983
Member
Registered: 2017-10-16
Posts: 11

Re: XSIBackup-DC is it possible to --check on a remote over SSH replica?

Ah figured it out, this worked for me:

https://helpcenter.onlyoffice.com/insta … scall.aspx

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#5 2021-07-28 12:04:11

d4t1983
Member
Registered: 2017-10-16
Posts: 11

Re: XSIBackup-DC is it possible to --check on a remote over SSH replica?

Just to add though, how does it check the data without looking at the source data on the source server?

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#6 2021-07-28 12:38:06

admin
Administrator
Registered: 2017-04-21
Posts: 1,821

Re: XSIBackup-DC is it possible to --check on a remote over SSH replica?

Great!, they block basic system calls. This must be the ultimate in security. Wait until they discover that blocking all of them is even more secure.

Our recommended distro is CentOS. Now that they took the turn of eliminating the stable CentOS releases we will switch to some other stable distro, most probably based in Debian.

We meant that you share the output of the --replica job that failed.

--check argument just checks that the blocks in the manifest exist in the replica and their hashes are correct. If you use the --replica=cbt plus --options=R, your remote VM will be registered and you can switch it on to check its contents.

If you receive some error in the middle of a backup, you should investigate where that error came from and whether that corrupted your mirror disks. As you seem to be quite confident, we guesss you received the error after 100% of the blocks had already been copied.

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#7 2021-07-28 12:41:19

d4t1983
Member
Registered: 2017-10-16
Posts: 11

Re: XSIBackup-DC is it possible to --check on a remote over SSH replica?

Well, least now you know wink (much like I do)

Ok I see. That's what I was trying to do if by what you call mirror disks you mean the mirrored data at the replica side?

I must admit I should of made a not of the error but I didn't, I'm pretty sure it was mid way through backing up too as I had to verify the xsibackup process wasn't present then manually delete the lock file.

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#8 2021-07-28 15:25:06

admin
Administrator
Registered: 2017-04-21
Posts: 1,821

Re: XSIBackup-DC is it possible to --check on a remote over SSH replica?

Then you should resync the whole VM. Delete all files at the target.
If you want some faster kind of replica and finer control on the data to transfer, you can use CBT (DC version only).
The first replica copies all data, then the CBT feature copies over just the blocks that have changed and skips the rest.
If later on you have some error of this kind, you can just use a lower CBT sequence number to resend all blocks from a given point in time.
Details on (c)XSIBackup CBT implementation

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#9 2021-07-28 15:26:51

d4t1983
Member
Registered: 2017-10-16
Posts: 11

Re: XSIBackup-DC is it possible to --check on a remote over SSH replica?

I was using CBT when it happened, does this mean I should still delete and resync the whole VM still?

Side question: Is it possible to compress data during transfer as it seemed to me like SSH compression is off by default?

Last edited by d4t1983 (2021-07-28 15:27:42)

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#10 2021-07-28 15:57:17

admin
Administrator
Registered: 2017-04-21
Posts: 1,821

Re: XSIBackup-DC is it possible to --check on a remote over SSH replica?

Just use some sequence number above 1, that should do it. If you had performed many CBT syncs, the closer to the failing sequence, the lower the amount of data to transfer. It might not be significant in your case, we don't know the amount of data generated in between CBT cycles.

SSH compression is disabled by default in both --replica and --backup, it's redundant and useless. In case of --backup because the data chunks themselves are already compressed by default. In case of --replica because zero blocks are filtered out and compression is only really significant when many zeros are present.

Compressing binary data where most zeros have already been stripped off makes no sense.

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#11 2021-07-28 16:06:21

d4t1983
Member
Registered: 2017-10-16
Posts: 11

Re: XSIBackup-DC is it possible to --check on a remote over SSH replica?

So with CBT all changes are tracked and kept historically for the whole time CBT is enabled?

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#12 2021-07-28 16:58:41

admin
Administrator
Registered: 2017-04-21
Posts: 1,821

Re: XSIBackup-DC is it possible to --check on a remote over SSH replica?

Not really, just a sequence integer associated to each block or zone in the disk. Given that you have the base data already on the remote end, transfering blocks greater than some value ensures that the remote disks contain the same changed data.

If some, let's say, ransomware infects your source disk you lose everything.

The only way to keep an unlimited number of real restore points is to use the --backup argument. Then using xsifs you can mount any of the restore points in Linux and access the data contained within them.

There's already a Beta preview of 1.5.1.0 featuring CBT on the --backup as well as in the --replica action.

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#13 2021-07-28 18:24:19

d4t1983
Member
Registered: 2017-10-16
Posts: 11

Re: XSIBackup-DC is it possible to --check on a remote over SSH replica?

I guess I need to do some more reading as to how the CBT tracking works exactly.

How do I get the preview version? Happy to feedback any issues I might encounter!

And thanks for all your help and advice!

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#14 2021-07-28 21:08:58

admin
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Registered: 2017-04-21
Posts: 1,821

Re: XSIBackup-DC is it possible to --check on a remote over SSH replica?

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#15 2021-07-29 08:33:45

d4t1983
Member
Registered: 2017-10-16
Posts: 11

Re: XSIBackup-DC is it possible to --check on a remote over SSH replica?

Perfect, thanks again for all your help I really appreciate it!

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