Extstore

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theonajim

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Feb 10, 2020, 2:30:09 PM2/10/20
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For extstore feature, are there guidelines on size to allocate for extstore file? For example, if the drive has 500 GB capacity, do we allocate all 500 GB, 250 GB (50%) or something like 70% to 90% of drive capacity?
Does extstore compaction require free space to re-write the extstore file? Is there a stats output that shows compaction is running?

Thanks
--Theo

dormando

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Feb 10, 2020, 5:40:08 PM2/10/20
to 'theonajim' via memcached
Hey,

If you want to play safe you can allocate up to 95% of the drive. The
limiter for how much storage you can use is by how much RAM you have
relatively. IE; if key+metadata takes 200 bytes per object, and values are
500 bytes, you need 200 bytes of RAM for every 500 bytes of disk space.

Compaction doesn't use extra space outside of the file, it uses pages
within the existing file.

I don't think there's a counter for when it's running but there're
counters for how often it's run. The actual compaction is extremely fast,
and at a default page size of 64 megabytes I doubt it'll take more than a
hundred milliseconds or per page.

-Dormando
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