>>>>> "Gionatan" == Gionatan Danti <g.danti@xxxxxxxxxx> writes: Gionatan> Il 2020-09-09 17:01 Roy Sigurd Karlsbakk ha scritto: >> First, filelevel is usually useless. Say you have 50 VMs with Windows >> server something. A lot of them are bound to have a ton of equal >> storage in the same areas, but the file size and content will vary >> over time. With blocklevel tiering, that could work better. Gionatan> It really depends on the use case. I applied it to a Gionatan> fileserver, so working at file level was the right Gionatan> choice. For VMs (or big files) it is useless, I agree. This assumes you're tiering whole files, not at the per-block level though, right? >> This is all known. Gionatan> But the only reason to want tiering vs cache is the Gionatan> additional space the former provides. If this additional Gionatan> space is so small (compared to the combined, total volume Gionatan> space), tiering's advantage shrinks to (almost) nothing. Do you have numbers? I'm using DM_CACHE on my home NAS server box, and it *does* seem to help, but only in certain cases. I've got a 750gb home directory LV with an 80gb lv_cache writethrough cache setup. So it's not great on write heavy loads, but it's good in read heavy ones, such as kernel compiles where it does make a difference. So it's not only the caching being per-file or per-block, but how the actual cache is done? writeback is faster, but less reliable if you crash. Writethrough is slower, but much more reliable. _______________________________________________ linux-lvm mailing list linux-lvm@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/linux-lvm read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
