| /dev/Bcache0 | /dev/Bcache1 | /dev/Bcache2 | /dev/Bcache3 | /dev/Bcache4 | Writethrough and writearound SSD's can be shared. Each cache device in writeback mode must only be used to cache a single backing drive, to avoid data loss if that SSD fails.Replace the example uuid's with the uuid's of your caches. Register the cache devices against your backing devices. Cache SSD's in writethrough and in writearound mode can be shared by multiple backing devices, as they do not cause data loss when they fail. To avoid data loss in case of a failing SSD, each backing device needs its own SSD if it is in writeback mode. The cache devices can be whole devices, partitions or any other standard block devices. Format the cache devices (This will typically be your SSD's). This will create /dev/bcache0, /dev/bcache1 and /dev/bcache2.Ģ. The backing devices can be whole devices, partitions or any other standard block devices. Format the backing devices (These will typically be your mechanical drives). | /dev/Bcache0 | /dev/Bcache1 | /dev/Bcache2 |ġ. Each HDD needs its own SSD, to avoid data loss if a SSD in writeback mode fails.Situation: 3 hard drives and 3 read/write cache SSD's # mkfs.btrfs -L STORAGE -f -d raid1 -m raid1 /dev/bcache0 /dev/bcache1 /dev/bcache2 /dev/bcache3 The -L argument defines the label of the filesystem. Both the data and the metadata is stored twice in the array, so there will be no data loss when a single hard drive fails. Replace the example uuid with the uuid of your cache. Register the cache device against your backing devices. Only one cache device can be added to a group of backing devices. The cache device can be a whole device, a partition or any other standard block device. Format the cache device (This will typically be your SSD). This will create /dev/bcache0, /dev/bcache1, /dev/bcache2 and /dev/bcache3Ģ. ![]() | /dev/Bcache0 | /dev/Bcache1 | /dev/Bcache2 | /dev/Bcache3 | # make-bcache -block 4k -bucket 2M -C /dev/sdk1 ![]() For example, using a HDD with 4k sectors and an SSD with an erase block size of 2MB this command would look like The bucket size should match the erase block size of the caching device with the intent of reducing write amplification. ![]() The block size should match the backing devices sector size which will usually be either 512 or 4k. In this example the default block and bucket sizes of 512B and 128kB are used. The cache device can be a whole device, a partition or any other standard block device The backing device can be a whole device, a partition or any other standard block device. Format the backing device (This will typically be your mechanical drive). Do not enable write caching, as that can cause data loss when the SSD failsġ. ![]() When a single hard drive fails, all data is lost.
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