Re: cephfs inode backtrace information

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]


Hi Patrick,

> The actual recommendation is to use a replicated pool for the default data pool. Regular hard drives are fine for the storage device.

But would it not be a better recommendation to put the default pool on SSDs?

* If you expect to have many small files on CephFS on HDD, seeking can be a huge bottleneck for balancing/recovery/scrubbing. E.g. on 500 million small files it easily takes 2 months to recover. My understanding is that CephFS makes at least 2 RADOS objects per file: One for the file contents, one for the inode info. By putting half of those objects on SSD, one could reduce the seek bottleneck by 2x. And from my other post, each such inode object only seems to be ~512 Bytes (though in Loïcs' post it's 32 KiB, not sure why that is, maybe some different minimum object size?).

* If you do not expect to have many small files, inode information should be so small that it doesn't hurt to put it on SSD either.

So it seems like a sane recommendation either way.

Related thread I posted:

What do you think?

Would it make sense to recommend this in the Ceph docs for all filesystems, even non-EC replicated HDD?
ceph-users mailing list -- ceph-users@xxxxxxx
To unsubscribe send an email to ceph-users-leave@xxxxxxx

[Index of Archives]     [Information on CEPH]     [Linux Filesystem Development]     [Ceph Development]     [Ceph Large]     [Ceph Dev]     [Linux USB Development]     [Video for Linux]     [Linux Audio Users]     [Yosemite News]     [Linux Kernel]     [Linux SCSI]     [xfs]

  Powered by Linux