On Tue, May 12, 2015 at 3:41 PM, Stefan Priebe - Profihost AG <s.priebe@xxxxxxxxxxxx> wrote: > > Am 12.05.2015 um 14:35 schrieb Eric Sandeen: >> On 5/12/15 7:01 AM, Stefan Priebe - Profihost AG wrote: >>> Hi, >>> >>> while cloud / vms usage become more and more popular and qemu now also >>> offers memory hot add and unplug, cpu hot add and unplug, we still >>> suffer from a missing xfs shrink. >> >> Filesystem shrink is a very different scenario than "cloud / vms" needs >> for hot memory & cpu plugging, IMHO. >> >>> I would like to continue to use XFS as it is a rock solid base since >>> around 10 years for us. >>> >>> But one missing piece in variable ressource usage for us is disk >>> shrinking. Is there any chance to get an xfs online shrinking? >> >> Under what circumstance does your workflow require a filesystem shrink? > > May be special but there are a lot of customers out there who do not > manager their ressources. So they've partners and partners of partners. > It happens quite often that the disk runs out of space and the customer > does not know what he can do as third parties control the waste of > space. So we are in the situation where we need to extent the partition > so the customer can continue his business. Later when the partner has > solved the issue (real world shows mostly 2 days - 3 weeks) the customer > wants to shrink again as he does not want to pay the space. > >> Honest question, I'm not challenging you, but I would like to understand >> what it is about shrink that is so critical it may cause you to stop using >> XFS. >> >> One thing about shrink - while i.e. ext4 supports it, the end result of >> a shrunk filesystem is a scrambled filesystem. All those heuristics that >> made the filesystem reasonably performant as it aged get thrown out the >> window as the fs scavenges for space into which to shrink the filesystem... >> >> That said, another option is to use the dm-thinp target, and allocate / >> de-allocate storage resources to the underlying block device as needed. > > We do so while using ceph and trim but the customer pays what he can > theoretically use and not what he uses in real. Ceph also does not > provide a way to show us the real usage of a rbd disk. > > Greets, > Stefan > Am I right in a guess that this indirect management issue is a primary reason for having online shrinking as a feature? You can use BTRFS at it is supporting in-place shrink and achieved enough stability with plain use-cases, with enough necessity. Of course having simular thing in an XFS would be quite awesome for a general purpose or for a visionary case, but the real-world need in such a feature is a bit limited, from at least cloud provider` point of view. _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
