Hi, First of all congratulations for bcache! Working on a SAN head here under Fedora 19. The stack looks like that: JBOD(SAS)->MDADM(RAID10)->SCST(BLOCKIO)->iSCSI(10G)->ESXi The SAN server contains an SSD that we use for writethrough only bcache. Initially, we had: - Backing: /dev/mdX (Raid10) - Caching: /dev/sda (SATA SSD) The server also has 32G of RAM which we're trying to use for caching as well. As we have no FS and do BLOCKIO only, the linux page_cache is out of the picture (as far as I know). The idea is then to use a ramdisk (either BRD or RapidDisk) and use it as part of the cache as well. An idea is to use btier in order to "join" together a RAM disk (tier0) and the SSD (tier1), and use this btier device as a bcache cacheset. Btier will then regularly promote the hot blocks from SSD to RAM and demote the cold blocks. I imagine this should bring meta into RAM as well. It's technically working (lab) but I would like some feedback and please tell me if we're going to hit a wall somewhere. Drawback is that every boot gets a new blank cache set (with a new UUID), but this can be easily managed. Other ideas are: - bcache over bcache - dm-cache over bcache Thanks for reading and for feedback. - Patrick -
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