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drbd-user: [DRBD-user] size of DRBD writes

[DRBD-user] size of DRBD writes

From: Tim Wood <twwood_at_nospam>
Date: Mon Mar 01 2010 - 22:10:59 GMT
To: drbd-user@lists.linbit.com

If I make a small update to a file, for example overwriting just the first
byte, will DRBD send the full disk block that was modified, or does it just
send the data for the actual write (1 byte)? Clearly the latter would be
more efficient, but I'm not certain it is possible.

If it is the first option, is it sending a 1KB disk block, or is the block
size determined by the file system-- 4KB in my case?

I ask because I'm trying to estimate the bandwidth that will be required by
an app when using drbd, and my plan had been simply use iostat to measure
the average block writes/second and then multiply by the size of a block.


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