+++ This bug was initially created as a clone of Bug #1471753 +++ Description of problem: Problem: Consider an EC volume with configuration 4 + 2. The stripe size for this would be 512 * 4 = 2048. That means, 2048 bytes of user data stored in one stripe. Let's say 2048 + 512 = 2560 bytes are already written on this volume. 512 Bytes would be in second stripe. Now, if there are sequential writes with offset 2560 and of size 1 Byte, we have to read the whole stripe, encode it with 1 Byte and then again have to write it back. Next, write with offset 2561 and size of 1 Byte will again READ-MODIFY-WRITE the whole stripe. This is causing bad performance because of lots of READ request travelling over the network. There are some tools and scenario's where such kind of load is coming and users are not aware of that. Example: fio and zip Solution: One possible solution to deal with this issue is to keep last stripe in memory. This way, we need not to read it again and we can save READ fop going over the network. Considering the above example, we have to keep last 2048 bytes (maximum) in memory per file. Version-Release number of selected component (if applicable): How reproducible: Steps to Reproduce: 1. 2. 3. Actual results: Expected results: Additional info: --- Additional comment from Worker Ant on 2017-07-17 08:24:29 EDT --- REVIEW: https://review.gluster.org/17789 (cluster/ec: Keep last written strip in in-memory cache) posted (#1) for review on master by Ashish Pandey (aspandey) --- Additional comment from Worker Ant on 2017-07-19 01:39:03 EDT --- REVIEW: https://review.gluster.org/17789 (cluster/ec: Keep last written strip in in-memory cache) posted (#2) for review on master by Ashish Pandey (aspandey) --- Additional comment from Worker Ant on 2017-07-23 04:47:53 EDT --- REVIEW: https://review.gluster.org/17789 (cluster/ec: Keep last written strip in in-memory cache) posted (#3) for review on master by Ashish Pandey (aspandey) --- Additional comment from Worker Ant on 2017-08-21 01:31:04 EDT --- REVIEW: https://review.gluster.org/17789 (cluster/ec: Keep last written strip in in-memory cache) posted (#4) for review on master by Ashish Pandey (aspandey) --- Additional comment from Worker Ant on 2017-09-18 06:45:22 EDT --- REVIEW: https://review.gluster.org/17789 (Problem: Consider an EC volume with configuration 4 + 2. The stripe size for this would be 512 * 4 = 2048. That means, 2048 bytes of user data stored in one stripe. Let's say 2048 + 512 = 2560 bytes are already written on this volume. 512 Bytes would be in second stripe. Now, if there are sequential writes with offset 2560 and of size 1 Byte, we have to read the whole stripe, encode it with 1 Byte and then again have to write it back. Next, write with offset 2561 and size of 1 Byte will again READ-MODIFY-WRITE the whole stripe. This is causing bad performance because of lots of READ request travelling over the network.) posted (#5) for review on master by Ashish Pandey (aspandey) --- Additional comment from Worker Ant on 2017-09-18 06:55:48 EDT --- REVIEW: https://review.gluster.org/17789 (cluster/ec: Keep last written strip in in-memory cache) posted (#6) for review on master by Ashish Pandey (aspandey) --- Additional comment from Worker Ant on 2017-09-22 04:26:54 EDT --- REVIEW: https://review.gluster.org/17789 (cluster/ec: Keep last written strip in in-memory cache) posted (#7) for review on master by Ashish Pandey (aspandey) --- Additional comment from Worker Ant on 2017-10-03 08:35:56 EDT --- REVIEW: https://review.gluster.org/17789 (cluster/ec: Keep last written strip in in-memory cache) posted (#8) for review on master by Ashish Pandey (aspandey) --- Additional comment from Worker Ant on 2017-10-03 13:51:33 EDT --- REVIEW: https://review.gluster.org/17789 (cluster/ec: Keep last written strip in in-memory cache) posted (#9) for review on master by Ashish Pandey (aspandey) --- Additional comment from Worker Ant on 2017-10-04 03:51:44 EDT --- REVIEW: https://review.gluster.org/17789 (cluster/ec: Keep last written strip in in-memory cache) posted (#10) for review on master by Ashish Pandey (aspandey) --- Additional comment from Worker Ant on 2017-10-05 06:30:10 EDT --- REVIEW: https://review.gluster.org/17789 (cluster/ec: Keep last written strip in in-memory cache) posted (#11) for review on master by Ashish Pandey (aspandey) --- Additional comment from Worker Ant on 2017-10-09 13:20:46 EDT --- REVIEW: https://review.gluster.org/17789 (cluster/ec: Keep last written strip in in-memory cache) posted (#12) for review on master by Ashish Pandey (aspandey) --- Additional comment from Worker Ant on 2017-11-10 17:16:13 EST --- COMMIT: https://review.gluster.org/17789 committed in master by ------------- cluster/ec: Keep last written strip in in-memory cache Problem: Consider an EC volume with configuration 4 + 2. The stripe size for this would be 512 * 4 = 2048. That means, 2048 bytes of user data stored in one stripe. Let's say 2048 + 512 = 2560 bytes are already written on this volume. 512 Bytes would be in second stripe. Now, if there are sequential writes with offset 2560 and of size 1 Byte, we have to read the whole stripe, encode it with 1 Byte and then again have to write it back. Next, write with offset 2561 and size of 1 Byte will again READ-MODIFY-WRITE the whole stripe. This is causing bad performance because of lots of READ request travelling over the network. There are some tools and scenario's where such kind of load is coming and users are not aware of that. Example: fio and zip Solution: One possible solution to deal with this issue is to keep last stripe in memory. This way, we need not to read it again and we can save READ fop going over the network. Considering the above example, we have to keep last 2048 bytes (maximum) in memory per file. Change-Id: I3f95e6fc3ff81953646d374c445a40c6886b0b85 BUG: 1471753 Signed-off-by: Ashish Pandey <aspandey>
REVIEW: https://review.gluster.org/18844 (cluster/ec: Keep last written strip in in-memory cache) posted (#1) for review on release-3.13 by Ashish Pandey
This bug reported is against a version of Gluster that is no longer maintained (or has been EOL'd). See https://www.gluster.org/release-schedule/ for the versions currently maintained. As a result this bug is being closed. If the bug persists on a maintained version of gluster or against the mainline gluster repository, request that it be reopened and the Version field be marked appropriately.