Hi
I am interested in combining BtrFS RAID-5 with erasure-coded replication
for HDFS. We have an implementation of Reed-Solomon replication for our
HDFS distribution called HopsFS (www.hops.io).
Some of the nice features of HDFS that make it suitable are:
* not many small files
* not excessive snapshotting
* can probably manage disks being close to capacity, as its globally
visible and blocks can be re-balanced in HDFS
What BtrFS could give us:
* stripping within a DataNode using RAID-5
* higher throughput read/write for HDFS clients over 10 GbE without
losing data locality (others are looking at stripping blocks over many
different nodes).
* true snapshotting for HDFS by providing rollback of HDFS blocks
I am concerned (actually, excited!) that RAID-5 is not production ready.
Any guidelines on how mature it is, since the big PR in Feb/March 2015?
What about scrubbing for RAID-5?
Is there anything else I should know?
Btw, here are some links i found about RAID-5:
UREs are not as common on commodity disks - RAID-5 is safer than assumed:
*<https://www.high-rely.com/blog/using-raid5-means-the-sky-is-falling/>https://www.high-rely.com/blog/using-raid5-means-the-sky-is-falling/*
*
Btrfs Linux 4.1 with 5 10K RPM spinning disks:
<http://www.phoronix.com/scan.php?page=article&item=btrfs-raid015610-linux41&num=1>http://www.phoronix.com/scan.php?page=article&item=btrfs-raid015610-linux41&num=1
*Raid*-*5 *Results: ~250 MB/s for sequential reads. 559 MB/s for
sequential writes.
*
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