On 8/28/20 12:46 PM, Roman Mamedov wrote:
On Thu, 27 Aug 2020 21:31:07 -0500
"R. Ramesh" <rramesh@xxxxxxxxxxx> wrote:
I have two raid6s running on mythbuntu 14.04. The are built on 6
enterprise drives. So, no hd issues as of now. Still, I plan to upgrade
as it has been a while and the size of the hard drives have become
significantly larger (a indication that my disks may be older) I want to
build new raid using the 16/14tb drives. Since I am building new raid, I
thought I could explore caching options. I see a mention of LVM cache
and few other bcache/xyzcache etc.
Once you set up bcache, it cannot be removed. The volume will always stay a
bcache volume, even if you decide to stop using caching. Which feels weird and
potentially troublesome, going through an extra layer (kernel driver) with its
complexity and computational overhead (no matter how small).
On the other hand LVM with caching turned off is just normal LVM, that you'd
likely would have used anyway, for other benefits that it provides.
Also my impression is that LVM has more solid and reliable codebase, but
bcache might provide a somewhat better the performance boost due to caching.
Thanks for the info on bcache. I do not think it will be my favorite. I
am going to try LVM cache as my first choice. Note that the new disks
will be spare disks for some time and I will be able to try out a few
things before deciding to put it into use.
One thing about LVM that I am not clear. Given the choice between
creating /mirror LV /on a VG over simple PVs and /simple LV/ over raid1
PVs, which is preferred method? Why?
Ramesh
