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PD 6.6, PDDO, bad dedupe, bad cache hits, slow backups

taso_stock
Level 4
Partner Accredited
Hi,

we had a for the most part well working NBU system with a NBU 6.5.3 master/media server on Linux, a NBU 6.5.3 media server on Linux and two NBU PureDisk 6.5.1 systems. Usually, all the NBU clients on this system are backing up their data through the PDDO on the media server to the first PureDisk device in the first stage. On the second stage, there is a duplication running to a second PureDisk device (directly between the two SPA ). We are using storage lifecycle policies (SLP) for that.

Some days ago, we updated the whole system and are now on NBU 6.5.4, PDDO 6.6 and PD 6.6.

After the update, all the jobs with smaller than 50GB in size were working, but we saw bad performance, bad dedupe and bad cache hits, not only on the first jobs after the update. It is still happening.

All jobs with 50GB in size or greater failed, but this could be solved meanwhile by changing maximum fragment size on the PureDisk STU to a value that is lower than the value in pd.conf (MAX_IMG_MBSIZE) on the PDDO!MAX_IMG_MBSIZE is remarked by default, which means, it's on 50.000 (MBytes).
So, we set the maximum fragment size on the PureDisk STU to 48 GBytes = 49.152 MBytes.

The current problem is:
All the Backup jobs are still taking around 40% longer and the dedupe rate has gone down from > 90% to around 30...70%.
Because of the bad dedupe, too much backup storage on the PureDisk is used.

Anyone here, who had similar problems and found a solution?

Matthias
4 REPLIES 4

teiva-boy
Level 6
You've called support about this right?

taso_stock
Level 4
Partner Accredited
Thank's for your reply.
Yes, Symantec support is involved.
But there are no solutions until today.
My hope was, someone else had similar problems and maybe an idea how to fix this....

Matthias

ElGringo
Level 6
Partner Accredited
This issues is kknown and can be solved by an EEB.
The support guy should give you this patch. I had similar issue...

Etrack 1853294: Back up speed for a PDDO backup that exceed 50 GB in size may degrade significantly. A PureDisk internal cache that is not properly refreshed causes this problem. This results in an elevated cache miss rate for all but the first backup fragment.

taso_stock
Level 4
Partner Accredited
there were not only backup speed issues. Also bad dedupe (maybe as a reason for the poor performance).
Etrack 1853294 is only speaking about performance problems.

Meanwhile I solved the problems by installing PureDisk 6.6 new from scratch.