Łukasz K wrote:
>>> Now space maps, intent log, spa history are compressed.
>> All normal metadata (including space maps and spa history) is always
>> compressed. The intent log is never compressed.
>
> Can you tell me where space map is compressed ?
we specify that it should be compressed in dbuf_sync_leaf:
if (dmu_ot[dn->dn_type].ot_metadata) {
checksum = os->os_md_checksum;
compress = zio_compress_select(dn->dn_compress,
os->os_md_compress);
os_md_compress is set to ZIO_COMPRESS_LZJB in dmu_objset_open_impl(), so the
compression will happen in lzjb_compress().
> I want to propose few optimalization here:
> - space map block size schould be dynamin ( 4KB buffer is a bug )
> My space map on thumper takes over 3,5 GB / 4kB = 855k blocks
A small block size is used because we typically have to keep the last block
of every space map in memory (as we are constantly appending to it). This is
a trade-off between memory usage and time taken to load the space map.
--matt
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