Re: backup manifests - Mailing list pgsql-hackers
| From | Suraj Kharage |
|---|---|
| Subject | Re: backup manifests |
| Date | |
| Msg-id | CAF1DzPW7fEsdj+hbD2tjG1X_4Qj7Qeg+ETU2AZOoT=Jgvazv2g@mail.gmail.com Whole thread Raw |
| In response to | Re: backup manifests (Rushabh Lathia <rushabh.lathia@gmail.com>) |
| Responses |
Re: backup manifests
|
| List | pgsql-hackers |
Hi,
Since now we are generating the backup manifest file with each backup, it provides us an option to validate the given backup.
Let's say, we have taken a backup and after a few days, we want to check whether that backup is validated or corruption-free without restarting the server.
Please find attached POC patch for same which will be based on the latest backup manifest patch from Rushabh. With this functionality, we add new option to pg_basebackup, something like --verify-backup.
So, the syntax would be:
./bin/pg_basebackup --verify-backup -D <backup_directory_path>
Basically, we read the backup_manifest file line by line from the given directory path and build the hash table, then scan the directory and compare each file with the hash entry.
Thoughts/suggestions?
Since now we are generating the backup manifest file with each backup, it provides us an option to validate the given backup.
Let's say, we have taken a backup and after a few days, we want to check whether that backup is validated or corruption-free without restarting the server.
Please find attached POC patch for same which will be based on the latest backup manifest patch from Rushabh. With this functionality, we add new option to pg_basebackup, something like --verify-backup.
So, the syntax would be:
./bin/pg_basebackup --verify-backup -D <backup_directory_path>
Basically, we read the backup_manifest file line by line from the given directory path and build the hash table, then scan the directory and compare each file with the hash entry.
Thoughts/suggestions?
On Tue, Nov 19, 2019 at 3:30 PM Rushabh Lathia <rushabh.lathia@gmail.com> wrote:
My colleague Suraj did testing and noticed the performance impactwith the checksums. On further testing, he found that specifically withsha its more of performance impact.Please find below statistics:
no of tables without checksum SHA256
checksum% performnce
overhead
with
SHA-256md5 checksum % performnce
overhead with md5CRC checksum % performnce
overhead with
CRC10 (100 MB
in each table)real 0m10.957s
user 0m0.367s
sys 0m2.275sreal 0m16.816s
user 0m0.210s
sys 0m2.067s53% real 0m11.895s
user 0m0.174s
sys 0m1.725s8% real 0m11.136s
user 0m0.365s
sys 0m2.298s2% 20 (100 MB
in each table)real 0m20.610s
user 0m0.484s
sys 0m3.198sreal 0m31.745s
user 0m0.569s
sys 0m4.089s54% real 0m22.717s
user 0m0.638s
sys 0m4.026s10% real 0m21.075s
user 0m0.538s
sys 0m3.417s2% 50 (100 MB
in each table)real 0m49.143s
user 0m1.646s
sys 0m8.499sreal 1m13.683s
user 0m1.305s
sys 0m10.541s50% real 0m51.856s
user 0m0.932s
sys 0m7.702s6% real 0m49.689s
user 0m1.028s
sys 0m6.921s1% 100 (100 MB
in each table)real 1m34.308s
user 0m2.265s
sys 0m14.717sreal 2m22.403s
user 0m2.613s
sys 0m20.776s51% real 1m41.524s
user 0m2.158s
sys 0m15.949s8% real 1m35.045s
user 0m2.061s
sys 0m16.308s1% 100 (1 GB
in each table)real 17m18.336s
user 0m20.222s
sys 3m12.960sreal 24m45.942s
user 0m26.911s
sys 3m33.501s43% real 17m41.670s
user 0m26.506s
sys 3m18.402s2% real 17m22.296s
user 0m26.811s
sys 3m56.653s
sometimes, this test
completes within the
same time as without
checksum.approx. 0.5% Considering the above results, I modified the earlier Robert's patch and added"manifest_with_checksums" option to pg_basebackup. With a new patch.by default, checksums will be disabled and will be only enabled when"manifest_with_checksums" option is provided. Also re-based all patch set.Regards,--Rushabh LathiaOn Tue, Oct 1, 2019 at 5:43 PM Robert Haas <robertmhaas@gmail.com> wrote:On Mon, Sep 30, 2019 at 5:31 AM Jeevan Chalke
<jeevan.chalke@enterprisedb.com> wrote:
> Entry for directory is not added in manifest. So it might be difficult
> at client to get to know about the directories. Will it be good to add
> an entry for each directory too? May be like:
> Dir <dirname> <mtime>
Well, what kind of corruption would this allow us to detect that we
can't detect as things stand? I think the only case is an empty
directory. If it's not empty, we'd have some entries for the files in
that directory, and those files won't be able to exist unless the
directory does. But, how would we end up backing up an empty
directory, anyway?
I don't really *mind* adding directories into the manifest, but I'm
not sure how much it helps.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company--Rushabh Lathia
--
Thanks & Regards,
Suraj kharage,
EnterpriseDB Corporation,
The Postgres Database Company.
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