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April 24th, 2015 02:00
NetWorker 8.1.2.1+ vs. DataDomain daily written pre-compr / dedup ratio
Hello Guys,
I have noticed an interesting thing in our NetWorker/DD environment: after upgrading NW server to 8.1.2.1+ I saw that the daily written pre-compressed data reported by the DD increased to approx. twice as much as before. In NetWorker reports nothing changed, so it was very surprising.
I opened SRs both to DD & NW support and finally they found the root cause:
The older nw versions wrote the data to the mtree root and then renamed them to put them to their final location. This is changed now and networker (or the boost library?) is using 'fastcopy' technology instead of renaming.
The fastcopy also counts in the daily written pre-compr. data amount, that's why I see higher numbers there.
I don't know what's the benefit of this new operating method, I'm still waiting for the answer from the support.
So, both products are working and reporting correctly from their perspective...
This situation is not considered as a bug, so the support offered me to raise a Request For Enhancement (btw. do you know how can I track it? RFE# 232445.)
If this won't change soon the DD reports will be very misleading, because we will see much higher daily dedup ratios, daily written data, etc. and if you are using the DD in a mixed environment these number will be totally useless..
Did you also noticed the same thing in your environment?
Best regards
Istvan
ble1
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April 24th, 2015 04:00
From which version did you upgrade? I was using DDBoost with NW7.6.x (it was possible with modules) and later on went to 8.0.x and now to 8.2.x, but I didn't see any changes. With that said, I usually only monitor space used so I could have missed pre-comp very easily as I'm not bothered by that number.
ionthegeek
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April 24th, 2015 06:00
This copy-and-delete behaviour is a change that was made in version 3.0.1.0 of the DDBoost library. The change was made because of an issue where a large number of ddp_rename operations could trigger a DDFS panic.
ble1
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April 24th, 2015 06:00
I assume that would indicate that NW is not so much related as much as it is ddboost on DD itself then? Is that since DDOS 5.5? (I think boost 3.x is since that verion, right?)
ble1
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April 24th, 2015 06:00
Sure, but in combination with NW, does pre-comp reflect data as seen kept by NW or as seen by DD? I still tend to keep these reports via NW, but I never tried to compare it to DD because normally I generate mminfo for previous day, load it into mysql and then I create end month report for each datazone (this data includes replication). That value most likely would never match what DD shows as my retention is 2 weeks so I assume pre-comp value would need to match (if in sync with NW) mminfo output for all datazones using that DD (and while I didn't check, I assume also those replicated onto the box). I don't use DDMC; I use backup and recovery manager to list those in one view and take screenshot for end month capacity overview. BRM is free while DDMC I was told is not. Regardless, I plan to start testing DPA soon which should contain pretty much same possibility for reporting (managing wise, I use CLI only).
oldhercules
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April 24th, 2015 06:00
@Ian:
We have DDOS 5.4.4.2, NetWorker 8.1.2.6 says he has libddboost 2.6.5.0.4 build 494492.. so now I'm a little bit confused
@Hrvoje: I agree that the really interesting number is the real free space, but it was really noticeable when I saw that on weekends the pre-compr. value is 160 TiB instead of 90.. it is (or it was...) also a good indicator to see how much data do we read from disks for backup reasons... We upgraded from nw8.0.2.6.
and some other things: as I know you are managing many DDRs, do you use the DataDomain Management Console appliance? You should try it, it needs only a small VM, (he says he is a DDVA, running DDOS :), and it has very nice historical perfomance graphs, alerting etc. (dd, mtree space consumption (even hourly), CPU usage, network load, replication info and streams info (this one is not working for us, but I had no time to open a SR yet...). You need to order a free licence from EMC sales rep. to deploy it.