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Hi Kevin,
On 1/17/2019 10:50 PM, KEVIN MICHAEL
HRPCEK wrote:
Hey,
I recall reading about this somewhere but I can't find it in the
docs or list archive and confirmation from a dev or someone who
knows for sure would be nice. What I recall is that bluestore
has a max 4GB file size limit based on the design of bluestore
not the osd_max_object_size setting. The bluestore source seems
to suggest that by setting the OBJECT_MAX_SIZE to a 32bit max,
giving an error if osd_max_object_size is > OBJECT_MAX_SIZE,
and not writing the data if offset+length >= OBJECT_MAX_SIZE.
So it seems like the in osd file size int can't exceed 32 bits
which is 4GB, like FAT32. Am I correct or maybe I'm reading all
this wrong..?
You're correct, BlueStore doesn't support object
larger than OBJECT_MAX_SIZE(i.e. 4Gb)
If bluestore has a hard 4GB object limit using radosstriper to
break up an object would work, but does using an EC pool that
breaks up the object to shards smaller than OBJECT_MAX_SIZE have
the same effect as radosstriper to get around a 4GB limit? We
use rados directly and would like to move to bluestore but we
have some large objects <= 13G that may need attention if
this 4GB limit does exist and an ec pool doesn't get around it.
Theoretically object split using EC might help. But
I'm not sure whether one needs to adjust osd_max_object_size
greater than 4Gb to permit 13Gb object usage in EC pool. If it's needed than tosd_max_object_size
<= OBJECT_MAX_SIZE constraint is violated and BlueStore
wouldn't start.
https://github.com/ceph/ceph/blob/master/src/os/bluestore/BlueStore.cc#L88
#define OBJECT_MAX_SIZE
0xffffffff // 32 bits
https://github.com/ceph/ceph/blob/master/src/os/bluestore/BlueStore.cc#L4395
// sanity check(s)
auto osd_max_object_size =
cct->_conf.get_val<Option::size_t>("osd_max_object_size");
if (osd_max_object_size >= (size_t)OBJECT_MAX_SIZE) {
derr << __func__ << " osd_max_object_size >= 0x" << std::hex << OBJECT_MAX_SIZE
<< "; BlueStore has hard limit of 0x" << OBJECT_MAX_SIZE << "." << std::dec << dendl;
return -EINVAL;
}
https://github.com/ceph/ceph/blob/master/src/os/bluestore/BlueStore.cc#L12331
if (offset + length >= OBJECT_MAX_SIZE) {
r = -E2BIG;
} else {
_assign_nid(txc, o);
r = _do_write(txc, c, o, offset, length, bl, fadvise_flags);
txc->write_onode(o);
}
Thanks!
Kevin
--
Kevin Hrpcek
NASA SNPP Atmosphere SIPS
Space Science & Engineering Center
University of Wisconsin-Madison
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Thanks,
Igor
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