Error copying files to Rados

E

ermanishchawla

Well-Known Member
Mar 23, 2020
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Steps to reproduce the issue
dd if=/dev/zero of=test4G bs=4M count=1024
1024+0 records in
1024+0 records out
4294967296 bytes (4.3 GB, 4.0 GiB) copied, 3.6726 s, 1.2 GB/s

rados -p vm2 put o9 test4G
error putting vm2/o9: (27) File too large

What is the size limit for rados??
 
According to the Ceph documentation, the max size for rados objects is 128Mb [1]. This is to prevent users directly adding objects with sizes that could negatively affect system behavior [2]. The manpage for rados also warns against using this command directly, and instead opting for one of their abstraction layers which automatically stripe data across objects, for example, see Ceph's File Striping explanation [3]

From the rados manpage 'put' description [4]:
"Warning: The put command creates a single RADOS object, sized just as large as your input file. Unless your objects are of reasonable and consistent sizes, that is probably not what you want -- consider using RGW/S3, CephFS, or RBD instead."

[1] https://docs.ceph.com/en/latest/rados/configuration/osd-config-ref/#confval-osd_max_object_size
[2] https://ceph-users.ceph.narkive.com/JExQaoQJ/rados-maximum-object-size-issue-since-luminous
[3] https://docs.ceph.com/en/latest/dev/file-striping/
[4] https://docs.ceph.com/en/latest/man/8/rados/#pool-specific-commands
 
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