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bio website comerford.cc
location Ireland
age 35
visits member for 2 years, 9 months
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I currently work for MongoDB, Inc. and have a background in operations, networking and system administration. You can find me in all the usual places, but probably the most useful and relevant are listed below:

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Mar
19
awarded  Citizen Patrol
Mar
11
answered MongoDB starting gets terminating
Mar
2
answered MongoDB: big size of mapped memory
Feb
27
answered MongoDB sharding authentication with multiple keyFile's
Feb
25
comment Why is mongod not using all available RAM?
If you take a look at the pieces related to under reporting of virtual memory you will note that it is possible for resident memory to be low, and not increase, but for data to be in memory. Pre-heat the data, then run a query, see if there are page faults when you know the data is in memory. You will probably need to quiesce the database to be sure about the measurement. If the secondaries are similarly spec'ed then do a failover and see what the behavior looks like then (this is what I meant about them all looking the same or not).
Feb
24
comment Why is mongod not using all available RAM?
OK, well it could be readahead, but it would have to be way off (very high/inefficient). NUMA is likely not a problem if you are using VMs. Page faults while the set is heating up is OK (after all, you have to have page faults to get the data into active memory) but once you have touched all the relevant data once, they should ease off. Hence my recommendation to pre-heat and then evaluate. If they do ease off, then it would seem you have a reporting issue with resident memory, if not then something else is going on. Do all VMs show the same limitation?
Feb
24
answered Why is mongod not using all available RAM?
Jan
28
answered Mongo Sharding - Config Server and Mongo Authentication
Jan
24
awarded  Yearling
Jan
8
revised Mongodb stats explanation
added 170 characters in body
Jan
8
answered Mongodb stats explanation
Dec
30
comment how can I install MongoDB as a service in centOS
minor follow up here - the OS repos tend to get out of date, and give you older versions (freezing on the major version for example). If you use the 10gen/MongoDB repos and packages instead (as described in the guide you linked) you will get the latest versions
Dec
27
answered Create MMS alert to monitor primary availability
Dec
27
answered Mongodump segmentation fault when dumping all dbs
Dec
5
answered mongo server does not start on Centos 6.4
Dec
3
comment How to calculate the required EBS PIOPS for our mongo server?
You didn't mention the instance size but I would expect single volumes to be able to do significantly more than 25 IOPS a piece (with 4 total you get the 100 figure I mentioned) - if you were seeing IOWait, high queues (and you don't seem to be) then I would expect a significant improvement. Without obvious IOPS related stress, the biggest improvement you will probably see is a reduction in peak latency (PIOPS performance is more predictable). You may get more bang for your buck getting more RAM so MongoDB can fit more data into memory and hit disk less often (depends on your usage pattern)
Dec
3
answered MongoDB Balancer
Dec
3
answered How to calculate the required EBS PIOPS for our mongo server?
Nov
26
comment Is it safe to snapshot an mdadm RAID with only xfs_freeze?
As long as the snapshot is point-in-time guaranteed you do not have to stop MongoDB (as long as the journal is included in the snapshot). Of course, that's independent of whether the snapshot itself is consistent from a data perspective across the volumes without freezing the data itself.
Nov
14
comment Spawning mongod process using sudo yields two separate mongod processes
I think the nature of the processes is answered below, but I will say this: do not start MongoDB as root, do not use sudo to run MongoDB - or any database for that matter - it is a bad, bad idea. If you switch to another user, as you should, you will have to manually fix the ownership on the various data files before the new user will be able to successfully start.