That is correct. The blocks of each recovery log are striped across the devices in the system.log pool (if it is defined). As a result, even when all clients have a local device in the system.log pool, many writes to the recovery log will go to remote devices. For a client that lacks a local device in the system.log pool, log writes will always be remote.
Notice, that typically in such a setup you would enable log replication for HA. Otherwise, if a single client fails (and its recover log is lost) the whole cluster fails as there is no log to recover FS to consistent state. Therefore, at least one remote write is essential.
HTH,
--
Vasily Tarasov,
Research Staff Member,
Storage Systems Research,
IBM Research - Almaden
----- Original message -----
From: Kenneth Waegeman <kenneth.waege...@ugent.be>
Sent by: gpfsug-discuss-boun...@spectrumscale.org
To: gpfsug main discussion list <gpfsug-discuss@spectrumscale.org>
Cc:
Subject: [gpfsug-discuss] system.log pool on client nodes for HAWC
Date: Tue, Aug 28, 2018 5:31 AM
Hi all,
I was looking into HAWC , using the 'distributed fast storage in client
nodes' method (
https://www.ibm.com/support/knowledgecenter/en/STXKQY_5.0.0/com.ibm.spectrum.scale.v5r00.doc/bl1adv_hawc_using.htm
)
This is achieved by putting a local device on the clients in the
system.log pool. Reading another article
(https://www.ibm.com/support/knowledgecenter/STXKQY_5.0.0/com.ibm.spectrum.scale.v5r00.doc/bl1adv_syslogpool.htm
) this would now be used for ALL File system recovery logs.
Does this mean that if you have a (small) subset of clients with fast
local devices added in the system.log pool, all other clients will use
these too instead of the central system pool?
Thank you!
Kenneth
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