On Thu, Nov 21, 2013 at 05:07:02PM -0800, Paul B. Henson wrote: > > From: David H. Rhodes Clymer > > Sent: Thursday, November 21, 2013 5:56 AM > > > > I have two bcache devices with different backing devices, but with shared > > cache. The backing devices are LVM logical volumes on top of an RAID1 > > software raid device (/dev/md2). The filesystem is ext4. > > Off-topic, sorry, but if I understand you your layering is: > > disks - mdraid - lvm - bcache - filesystem? > > So you created an lv which is the backing device for bcache? > > I've been looking at using bcache, but I was planning on switching the > ordering and putting bcache on top of the mdraid, then creating a pv for lvm > on the bcache device: > > disks - mdraid - bcache - lvm - filesystem > > Out of curiosity, I was wondering why you layered the other way.
Laziness, mostly. The RAID1 array is a PV that houses filesystems we'd rather thot lose. The development databases are not so critical - we rebuild them at least once a week anyway. The use of LVs was a quick and easy way to test various caching implementations without increasing the risk of data loss or corruption in the rest of the system. If you want to provide a block cache for all of your logical volumes, it would make much more sense to put LVM on top of bcache rather than the other way around. -davidc -- To unsubscribe from this list: send the line "unsubscribe linux-bcache" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
