On 13/01/20 12:10, Carlos Maiolino wrote:
First of all, I think there is no 'right' answer, but instead, use what best fit you and your environment. As you mentioned, there are PROs and CONS for each different solution. I use XFS reflink to CoW my Virtual Machines I use for testing. As I know many others do the same, and it works very well, but as you said. It is file-based disk images, opposed to volume-based disk images, used by DM and LVM.man. About your concern regarding fragmentation... The granularity is not really 4k, as it really depends on the extent sizes. Well, yes, the fundamental granularity is block size, but we basically never allocate a single block... Also, you can control it by using extent size hints, which will help reduce the fragmentation you are concerned about. Check 'extsize' and 'cowextsize' arguments for mkfs.xfs and xfs_io.
Hi Carlos, thank you for pointing me to the "cowextsize" option. From what I can read, it default to 32 blocks x 4 KB = 128 KB, which is a very reasonable granularity for CoW space/fragmentation tradeoff.
On the other hand, "extsize" seems to apply only to realtime filesystem section (which I don't plan to use), right?
Thanks. -- Danti Gionatan Supporto Tecnico Assyoma S.r.l. - www.assyoma.it email: g.danti@xxxxxxxxxx - info@xxxxxxxxxx GPG public key ID: FF5F32A8
