2,924 reputation
631
bio website comerford.cc
location Ireland
age 35
visits member for 2 years, 11 months
seen 13 hours ago

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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Apr
3
comment Did my mongoDB server crash because the database is too large?
@Tim - mongodb has a max file size of 2GB for that reason (some FS/OS not supporting it) - it pre-allocates multiple files of 2GB (max, starts smaller) when databases exceed that size (see your data directory for database.0, database.1 etc.)
Mar
31
answered Copy mongodb collection between two servers AND different mongo versions …
Mar
28
comment MongoDB and ZFS bad performance: disk always busy with reads while doing only writes
@jlliagre - yes, but as soon as you start actually changing the file you are going to see a performance hit, because you invalidate the whole lot
Mar
28
awarded  Nice Answer
Mar
28
revised Remove a secondary from a mongo replica set without triggering re-election?
Original poorly explained why this is the case, also added a link to the enhancement to improve the behavior
Mar
27
comment MongoDB and ZFS bad performance: disk always busy with reads while doing only writes
@AlexF - yes, basically - the server ticket I pointed to is the one that will fix that particular issue for ZFS on Linux. You can see a similar check for NFS here already, so it should not be a huge change, but there are likely to be other issues: github.com/mongodb/mongo/blob/v2.4/src/mongo/util/…
Mar
25
answered MongoDB and ZFS bad performance: disk always busy with reads while doing only writes
Mar
20
awarded  Revival
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