Daniel; How is your pool configured? Replica, or Erasure-Coded? I don't actually know any of this, but... I would expect that a synchronous call to a replica pool (R=3) would look something like this: Client --> PG Master Host (data) PG Master Host --> Local Disk (data) PG Master Host --> PG Replica Host 1 (data) PG Master Host --> PG Replica Host 2 (data) PG Replica Host 1 --> Disk (data) PG Replica Host 2 --> Disk (data) PG Replica Host 1 --> PG Master Host (ack) PG Replica Host 2 --> PG Master Host (ack) PG Master Host --> Client (ack) Some of that can happen in parallel, for instance the master could be transferring the file to both replica hosts, while also writing it to disk. You can imagine why a synchronous call could be significantly slower though, yes? Thank you, Dominic L. Hilsbos, MBA Director – Information Technology Perform Air International, Inc. DHilsbos@xxxxxxxxxxxxxx www.PerformAir.com -----Original Message----- From: Daniel Mezentsev [mailto:dan@xxxxxxxxxx] Sent: Friday, July 17, 2020 3:05 PM To: ceph-users@xxxxxxx Subject: ceph/rados performace sync vs async Hi All, I started a small project related to metrics collection and processing, Ceph was chosen as a storage backend. Decided to use rados directly, to avoid any additional layers. I got a very simple client - it works fine, but performance is very low. Can't get more than 30-35MBsec. Rados bench shows 200MBsec for my test pool. Should be mentioned about the client - I'm using sbcl (yep lisp). Call to rados API is just cffi call. Did try in async mode. Wow ! Saturated network bandwidth for large objects (4Mb and bigger), for small objects - saturated OSD IOPS ~2.4KIOPS for 8 SAS disks, so ~300 IOPS per disk - that sounds pretty reasonable. Bottom line - issue not with the lisp client - im getting close to C performance, difference is sync vs async IO. Why it's so big - sync operations are approx 2-3 times slower then async . Daniel Mezentsev, founder (+1) 604 313 8592. Soleks Data Group. Shaping the clouds. _______________________________________________ ceph-users mailing list -- ceph-users@xxxxxxx To unsubscribe send an email to ceph-users-leave@xxxxxxx _______________________________________________ ceph-users mailing list -- ceph-users@xxxxxxx To unsubscribe send an email to ceph-users-leave@xxxxxxx
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