No need with xfs.-- Dave • When growing a raid0 device, the new component disk size (or external backup size) should be larger than LCM(old, new) * chunk-size * 2, where LCM() is the least common multiple of the old and new count of component disks, and "* 2" comes from the fact that mdadm refuses to use more than half of a spare device for backup space. If using ext3/4, be sure to calculate your stripe-width when you format the FS. mdadm -E /dev/sda1 or similar against one of the devices in the array. It will print the superblock and lists the chunk size there. (As a side-note, please take into account that the mdadm manual page, as of the date of writing this part, states that the default chunk size is 512 KiB.) it is for the OS, which probably contain a lot of small files. mdadm: Note: this array has metadata at the start and may not be suitable as a boot device. 2. which is the best chunk size for raid 5, which will contain a lot of big files (1-2gb)? It includes 128 KB for the RAID superblock. The mdadm tool will start to mirror the drives. In order to get the best array performance, you need to know the correct chunk size and the golden rule for choosing it: small inputs / outputs = large chunk, and large inputs / outputs = small chunk. Replace SIZE with an integer value in kilobytes for the desired size. Cache Cache is simply RAM, or memory, placed in the data path in front of a disk or disk array. 2) executing the "mdadm --create ..." command using different options (see bellow for list) than have been used when array have been created originally:-> different chunk size -> different layout -> different disks order 3) resync-ing the array It would be different if you had 20+devices, but for 3 devices, you're probably fine. Chunk size; Let's look at all three. For example: Chunks: the hidden key to RAID performance (from 2007), which suggests quite small chunks by today's standard; The chunk size is a property of the RAID array, decided at the time of its creation. (A kilobyte is 1024 bytes.) 64k is default in mdadm. M. It can be found with mdadm: # mdadm --detail /dev/mdX | grep 'Chunk Size' Mdadm (pronounced "m-d-adam") is a tool for Linux for managing software RAID devices in Linux. Increasing the stripe width adds more disks and can improve read/write performance if the stripe width (chunk size) is greater than the data size. y. Note that the switch is -E, not -e. See the third grey section here. mdadm --create --verbose /dev/md0 --level=linear --raid-devices=2 /dev/sdb6 /dev/sdc5 should create the array. If you plan to store '/boot' on this device please ensure that your boot-loader understands md/v1.x metadata, or use --metadata=0.90 mdadm: size set to 104792064K Continue creating array? These are derived from the RAID chunk size, the filesystem block size, and the number of "data disks". thanks a lot. The parameters talk for themselves. 1. which is the best chunk size and best configuration for raid 0? For example, the following command sets the segment size for each RAID device to about 40 GB where the chunk size is 64 KB. EDIT: See here and here on chunk size in RAID1 mdadm's current default is 512 KiB. Have a look in /proc/mdstat. There used to be a lot of hand tuning with nested raid configs, chunk-size, etc, but these days you can pretty much just throw a --level=5 at it and be fine. The RAID chunk size refers to those parts of the strip into which it is divided. The output might look like this mdadm: chunk size defaults to 64K mdadm: array /dev/md0 started. You … Of big files ( 1-2gb ) format the FS like this mdadm: chunk size to. Raid array, decided at the time of its creation decided at the of... 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