Mdadm chunk size. The default when creating an array is 512KB.

Mdadm chunk size 512k) stride: stripe size / block size (ex. A Comparison of Chunk Size for Software RAID-5 Linux Software RAID Performance Comparisons The Problem Many claims are made about the chunk size parameter for mdadm (--chunk). 1 and 3. I used 2 partitions to create a RAID1 array. 9GB Sector size (logical/physical): 512B/512B Partition Table: msdos Number Start End Size Type File system Nevertheless, a linear array might be smaller than the sum of the sizes of the component devices because MD devices use a chunk size. I've previously asked For RAID 5, RAID 50, RAID 6, or RAID 60, a stripe size between 256k and 512k would be ideal for tube sites and large file download sites hosted on hard drives, while a stripe size between 128KB and 256KB would be better . 90 Creation Time : Fri Dec 24 19:32:21 2010 Raid Level : raid5 Array Size : 17581562688 (16767. The difference is that it creates an array without a superblock. RAID 5 is similar to RAID-4, except the parity info is spread across all drives in the array. Update bitmap: Mark the RAID chunks that were just written as clean. I intend to create: mdadm --create /dev/md0 --level 1 Menu. x cannot mdadm --create /dev/md0 --level=10 --raid-devices=4 /dev/sda1 /dev/sdb1 /dev/sdc1 /dev/sdd1 Devices : 4 Working Devices : 4 Failed Devices : 0 Spare Devices : 0 Layout : sudo mdadm --create --verbose /dev/md0 --level=5 --raid-devices=3 /dev/sda dev/sdb /dev/sdc mdadm: layout defaults to left-symmetric mdadm: layout defaults to left # mdadm --create --verbose /dev/md0 --level=5 --raid-devices=3 /dev/loop0 /dev/loop1 /dev/loop2 mdadm: layout defaults to left-symmetric mdadm: layout defaults to left-symmetric mdadm: mdadm: chunk size defaults to 512K mdadm: Defaulting to version 1. both of them are 967131168 sectors, 512 bytes per sector. Ask Question Asked 2 years, 10 months ago. Full in raid 5 you should look about raid chunk size. but it shows: Array Size : Improve mdadm RAID5 with SSD Cache. 46 GB) Used Dev Size : I currently am stuck at creating the 2-disk RAID5 array. The optimal RAID chunk size is a function of how you use the drive over longer periods mdadm で 5個の Volume を RAID 0 でストライピングしている状態 6 Failed Devices : 0 Spare Devices : 0 Chunk Size : 4K Consistency Policy : none Name : lvm01:mdadm-vol01 (local to $ sudo mdadm --detail /dev/md0 /dev/md0: Version : 0. When I created the partition, the optimal stripe unit and width values root@server# mdadm -v --grow --raid-devices=15 /dev/md0 mdadm: component size must be larger than chunk size. Wir betrachten dabei ein SW-Raid-Array (md-Raid), dass mit Hilfe von “mdadm” erstellt wurde. And if possible a full 500-600mb/s read. com/roelvandepaar Use the mdadm --grow mode to force the RAID to use a smaller segment size. Forums. everything i've found to read on the subject says that's determined by how big the files you're working with are. Ok. 04 VM. CHUNK-SIZE The presence of a '--run' can override this\n" " caution. 2 Creation Time : Thu Nov 30 12:18:58 2023 Raid Level : raid6 Used Dev Size : 1953382400 (1862. 00 Mdadm should default to 256K or 512K chunks. The varying chunk size for software RAID was required to show peak 4K transfer speeds in an optimized configuration and peak large # mdadm -CR /dev/md0 -l5 -n3 /dev/sd[abc] --assume-clean --size 1G # mdadm -D /dev/md0 From the Chunk Size drop-down list, select the size from the list of available options. 52 GB) For optimal performance, you should experiment with the chunk-size, as well as with the block-size of the filesystem you put on the array. A single drive provides a read Use the mdadm --grow mode to force the RAID to use a smaller segment size. The chunk size of the raid is 512 KB. The smaller chunk sizes increased my plot times by 3-4 mins (64) compared to Mdadm default $ mdadm --detail /dev/md0 /dev/md0: Version : 1. they have been wiped, if that's the case it doesn't explain this mdadm: super1. With RAID volumes, the chunk size is called a “stripe unit size. The Chunk Size value specifies how large each block is for mdadm is a Linux utility used to manage software RAID devices. You can read or write RAM about 100,000 times $ sudo mdadm --detail /dev/md0 /dev/md0: Version : 1. -c, --chunk= Specify Usage: mdadm--build md-device--chunk=X--level=Y--raid-devices=Z devices This usage is similar to --create. There are many discussions and websites that explain the process of setting up a Linux software RAID with mdadm with the chunk size of a new RAID as 128kBs or 512Kbs. 2. RAID-0 can, in many cases, help IO performance Update bitmap: Mark the RAID chunks you are about to write to as dirty. 2 Creation Time : Thu Sep 29 17:07:10 2022 Raid Level : raid10 Array Size : 209582080 (199. Obviously some of these are synonymous. . 32 GB) Used Dev Size : Trying to assemble the array now, mdadm keeps reporting device or resource busy - and yet its not mounted or busy with anything to my knowledge. 1 - @CircusCat Those optimisations in the block device driver are not perfect for large mdadm chunk sizes: I created a RAID5 with 4 disks and chunk size 4M and copied 37. so the raid array size should be 483564544. RAID devices are made up of multiple storage devices that are 0 Layout : -unknown- Chunk Size : 512K Linux Software RAID (MDADM, MDRAID) can be used as an underlying storage device for StarWind Virtual SAN devices. to mdadm: chunk size defaults to 512K mdadm: array /dev/md0 started. There is poor documentation indicating if a chunk is per drive or The answer to the OP's question is: Yes. 4-1? Will I get an option of chunk size when installing ubuntu server in raid0 or will it just setup the default chunk size • 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 UPDATE 1: mdadm chunk size is 32K Writing to a single block device starts at 2. Would offset with max mdadm --examine /dev/sdf* mdadm: No md superblock detected on /dev/sdf NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT sda 8:0 0 447. sdd[0] 209584128 blocks super 1. I built the array # mdadm --create --verbose /dev/md0 --level=5 --raid-devices=2 /dev/sdc1 /dev/sdb1 mdadm: layout Now mdadm cannot change the chunk size on a raid10 post creation, so I'm stuck. 89 GiB 2000. Chunk-sizes for kernels that do that (if any exist) would then have stripe size (same as mdadm chunk size, ex. 0, it used a "chunk size factor" where 0=4KiB, 1=8KiB (2^x*4096) so it cannot be done on older kernels at Code: Model: ATA ST3000DM001-9YN1 (scsi) Disk /dev/sdf: 3001GB Sector size (logical/physical): 512B/4096B Partition Table: gpt Disk Flags: Number Start End Size File $ sudo lsblk -o NAME,SIZE,FSTYPE,TYPE,MOUNTPOINT. 2k次。存储中的一个重要角色，RAID独立冗余磁盘阵列,从分类上将有两种：基于raid卡的硬raid(硬件实现，速度高，适用于大型应用)，基于系统的软raid(一般包 sudo mdadm --verbose --create /dev/md0 --level=0 --raid-devices=3 /dev/sdc /dev/sdf /dev/sde mdadm: chunk size defaults to 512K mdadm: /dev/sdc appears to contain an ext2fs file system I want to create (and test) mdadm raid10 with 4 nvme enterprise ssd's in 2 mirrors striped (raid10). 2 Creation Time : Sun Jan 6 02:09:29 2019 Raid Level : raid6 Array Size : 9764963840 (9312. For others experiments and 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. to change it run : How to tell mdadm to use a partition as/instead of a block-device? 4. One might think that this is the minimum I/O size across which parity can be computed. 64k / 4k = 16) stripe-width: stride * #-of-data-disks (ex. 1G 0 disk ├─sda1 8:1 0 200M 0 part /boot/efi ├─sda2 8:2 0 1G 0 part /boot └─sda3 I have a 9TB XFS partition consisting of four 3TB disks in a RAID-5 array with a chunk size of 256KB, using MDADM. One might think that this is the minimum # parted -l Model: VMware, VMware Virtual S (scsi) Disk /dev/sda: 85. 1 GB, 480103981056 bytes, 937703088 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size Further chunks are gathered into stripes in the same way, and are assigned to the remaining space in the drives. 4. The address space of the array is conceptually divided into chunks and The optimal RAID chunk size is not something you can "discover" from the drive itself. 2 Creation Time : Mon May 1 12:00:00 2023 Raid Level : raid5 Array Size : 30000 (29. Do this: mdadm --assemble --run /dev/md0 LOOPDEVICE1 LOOPDEVICE2 The --run flag is what forces mdadm to assemble an md RAID array without all the devices. Use the mdadm --grow mode to force the RAID to use a smaller segment size. If devices in the array are not all the same size, then once the The mdadm tool did not handle expansion of arrays which were not chunk size aligned. 4096) stripe size (same as mdadm chunk size, ex. mdadm --grow --chunk=128 /dev/md0. For an array of N partitions, you need a file of size at least (N+1)*512KB. This comprehensive guide will walk you through the process of the man page for mdadm says: "[chunk] is only meaningful for RAID0, RAID4, RAID5, RAID6, and RAID10. Trouble is, component_size 15 Failed Devices : 0 Try to avoid mdadm --create to recover a RAID. 60 GiB 9999. 6. This is writable, but there are upper and lower limits (32768, 16). or use --metadata=0. Home. I recently changed the disks in my RAID5 from 3x2TB to 3x3TB. 2 Creation Time : Wed Jan 12 13:36:39 2022 Raid Level : raid5 Array Size : 20951040 (19. To do this, you must use the -z option to specify the amount of space in kilobytes to use from each device in Now, it is possible to change the chunk size of an existing RAID array by running. in parallel, then the remaining 4 kB to disk 0. 2 metadata mdadm: RUN_ARRAY failed: Invalid argument. raid0: mdadm –assemble /dev/md0 /dev/sda1 /dev/sdb1 使用sda1和sdb1创建RAID0，条带大小是64KB: mdadm What is the default chunk size for mdadm 2. Please note the following output or 152248005 blocks of 1024 bytes is consistent with the size mdadm --grow and resize2fs are reporting for md2. conf file will be Am I correct that optimal chunk size is average file read/written to disk divided by number of block devices in RAID array storing the data? For example if the average file size is 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. Write the data to the RAID. When running Cassandra on Azure, it's common to create an mdadm stripe set (that is, RAID 0) of multiple data disks to increase the overall disk [root@xuegod63 ~]#yum -y install mdadm [root@xuegod63 ~]# mdadm -C -v /dev/md0 -l 0 -n 2 /dev/sdb /dev/sdc -C 创建 -v 详细信息 -l 阵列级别 -n 阵列成员数量 mdadm: chunk size defaults to 512K mdadm: Defaulting to Chunk size can be modified, however it could be very slow process (and you should definitely backup all data before doing so, it will rewrite all data on disks). Optimizing ext2 filesystem for use on LVM + RAID device? Stride, stripe-width, LVM IO size considerations. Did you initially create these partitions with a smaller size, then later 等价于chunk size，但linear设备的chunk不是条带分布在所有磁盘上，第一个磁盘分布完后，再分布到第二个磁盘上。举例：mdadm --create /dev/md1 -llinear -n2 /dev/sdb /dev/md0: Version : 1. 2 512k chunks unused mdadm --grow /dev/mdX --size max Finally, restore the bitmap if you were using one. I've previously asked stripe_cache_size + stripe_cache_size (raid4, raid5 and raid6) number of entries in the stripe cache. 64 TiB, 4000787030016 bytes, 7814037168 sectors Disk model: HGST HUS724040AL Units: sectors of 1 * 512 = 512 bytes Sector size 文章浏览阅读1. it does not apply for raid1. The chunk size of the array is mdadm --create --verbose /dev/md0 --level=linear --raid-devices=2 /dev/sdb6 /dev/sdc5 should create the array. Cache Cache is simply RAM, or memory, placed in the data path in front of a disk or disk array. I glanced over mdadm's manpage now and it still says: Currently supported growth options including changing the Hi all, Does anybody know how to create a RAID10 with 4 USB devices on Jetson Nano? The following is my way with the error: # sudo apt-get install mdadm -y # sudo mdadm The default chunk size currently used by mdadm is 512KB. \n" " If no --size is given, the apparent size of the smallest I then can translate this offset to a disk and a offset on that disk, because I know the data start offset of md0 (2048 * 512), the chunk size (512K) and the layout (left-symmetric). 4 The manpage for mdadm describes a -c, --chunk= parameter, quoted below, that seems to relate to the RAID 0 stripe size. Google reported that dmraid is a possible Chunk-size could at most affect sector allocations on the disk, meaning that the allocation of files is done in chunk-sized units. In a RAID, a "chunk" is the minimum amount of data read or written to each data disk in the array during a single read/write operation. CHUNK-SIZE root@vod0-iva:/dev# mdadm --create /dev/md11 -v --raid-devices=2 --level=0 /dev/md1 /dev/md2 mdadm: chunk size defaults to 512K mdadm: /dev/md1 appears to be part The filesystem block size (cluster size for NTFS) is the unit that can cause excess waste for small files. 87 GiB 214. Linux software RAID with mdadm is used. A jpeg or video is good as it provides relatively unique See ‘--write-behind=’ (man mdadm) [stripe_cache <sectors>] Stripe cache size (RAID 4/5/6 only) [region_size <sectors>] 8:49 - 8:65 - 8:81 # RAID4 - 4 data drives, 1 parity (with metadata When creating a RAID0 of three 5TB drives into one 15TB media-files volume, what is the optimal chunk-size? 16k, 32k, 64k, 128k or 256k? The video-files range from 5gb - 30gb in size. While the wiki is not exactly clear on the meaning of the bitmap chunk • 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 We’ll use the mdadm command (multi-disk administrator): # mdadm --verbose --create /dev/md0 --level=0 --raid-devices=2 /dev/sdb1 /dev/sdc1 mdadm: chunk size defaults to 512K mdadm: Defaulting to version The chunk size determines how large such a piece will be for a single drive. 6GBps, then hovers at 1. 94 GiB # mdadm --create --verbose /dev/md0 --level=0 --raid-devices=2 /dev/sda1 /dev/sdb1 mdadm: chunk size defaults to 64K mdadm: array /dev/md0 started. Die Daten, die auf einem Opensuse-System gewonnen wurden, unterstreichen /dev/md0: Version : 1. Check mdadm manual page, there are two important notes, size units (may depend on mdadm version) and reserved The presence of a '--run' can override this\n" " caution. Modified 2 years, 10 months ago. 5 GB from /dev/zero to the md device (dd with bs=384k What would be the best chunk size and should it be near/far/offset? I was hoping to get near 300m/b read/write. 4GBps Writing to /dev/md0 starts at 1. 26 GB) Raid Devices : 10 Total Devices # mdadm --detail /dev/md0 /dev/md0: Version : 1. \n" " If Hi, I just installed Fedora 40 KDE Desktop and I have 3 disk (sdb,sdc,sdd) in RAID5 but mdadm fails to assemble the array: $ sudo mdadm -Asv mdadm: looking for devices for All you need to do is to create the correct /etc/raidtab and /etc/mdadm. conf file (which are persistent over reboots as they are a symlinks ultimately to ソフトウェアRAIDの構築とその管理を行うソフトウェアである “mdadm 114/117 pages [456KB], 65536KB chunk unused devices: <none> MIN RM SIZE RO TYPE Usage: mdadm--build md-device--chunk=X--level=Y--raid-devices=Z devices This usage is similar to --create. For example: if you choose a chunk size of 64 KB, a 256 KB file will use four chunks. active raid0 sdc[1] sdd[0] 209584128 blocks super 1. -h , (in Kibibytes) of space to use from each drive in RAID I played around with chunk sizes, 64, 256, 512 (default), 1024, and 2048. 5 TB, and changes again to 16 KB blocks for volumes above 35 TB, etc. I know For stripe size, we used a 4K stripe for Graid, with 4K, 64K, and 512K chunks for mdadm. 2 metadata mdadm: array /dev/md0 started. 5 TB Seagate Barracude Green drives (4k sectors). Looking at the resulting share in Windows, it reports: Size: 618GB Size on disk: Using mdadm to detect and assemble arrays — possibly in an initrd — is substantially more flexible and should be preferred. patreon. resync-ing The phrases block size, chunk size, stripe length or granularity will sometimes be used in place of stripe size but they are all equivalent. even if you pass the value, it will say ignoring chunk When I have created the file system I made sure to specify the stride-size and sripe-width (as recommended in some guide that I had read). x cannot open /dev/sdc: Device or the Chunk size options are: 16K, 32K, 64K, 128K, or 256K. 64k) stride: stripe size / block size (ex. 08 GiB 18003. --type cache-pool --cachemode writethrough - The chunk size changes to 8 KB blocks for HFS+ volumes larger than 17. \n" "\n" " If the --size option is given then only that many kilobytes of each\n" " device is used, no matter how big each device is. 1. mdadm: chunk size defaults to 512K mdadm: Defaulting to version 1. The output might look like this mdadm: the man page for mdadm says: "[chunk] is only meaningful for RAID0, RAID4, RAID5, RAID6, and RAID10. The advantage of The mdadm utility can be used to create and manage storage arrays using Linux’s software RAID capabilities. For any SSD chuck size must be 8 KiB I am trying to create a software raid5 array using mdadm: $ linux # mdadm --create --verbose /dev/md0 --level=5 --raid-devices=4 --spare-devices=0 /dev/sda1 /dev/sdb1 /dev/sdc1 Last time I checked, mdadm won't let you --grow raid10. The default when creating an array is 512KB. 55 GiB 40007. RAID 5 has a parity chunk that has to be updated alongside the data. The name is derived from the md (multiple device) device nodes it administers or manages, and it replaced The state of array was in active-checking, stuck at 99. ” Another term, Tested expanding a raid-10 on a ubuntu 16. It would be different if $ mdadm --detail /dev/md0 /dev/md0: Version : 1. Linux mdraid mdadm: chunk size defaults to 512K mdadm: array /dev/md0 started. The array was build with a chunk size of 256KB, mdadm is on version v4. 2 Creation Time : Wed Nov 10 18:05:57 2021 Raid Level : raid0 Array Size : 39069465600 (37259. 8GBps, then falls to 1. The mdadm man page is a bit cryptic about the chunk size and raid1:-c, --chunk= Specify chunk size of kibibytes. 30 GiB 31. The output might look like this mdadm: We would like to show you a description here but the site won’t allow us. I also wanted to change the chunk size from default 512k to 128k. To do this, you must use the -z option to specify the amount of space in kilobytes to use from each device in mdadm: layout defaults to left-symmetric mdadm: layout defaults to left-symmetric mdadm: chunk size defaults to 512K mdadm: partition table exists on /dev/sda mdadm: The general approach to recovery would be using mdadm --build with a chunk size of 64K (the old mdraid default, it changed to 512K later), the number of your devices and your presumed RAID $ fdisk -l Disk /dev/sdd: 3. 13 GB) CHUNK-SIZE AND LAYOUT CHANGES¶ Changing the chunk-size of layout without also changing the number of devices as the same time will involve re-writing all blocks in-place. mdadm manual from Fedora 15 has a CHUNK-SIZE AND LAYOUT CHANGES section. 512KiB ist übrigens auch die Steps to configure software raid 5 array in Linux using mdadm. 512k / 4k = 128) stripe-width: stride * #-of-data-disks (ex. 45 GB) Used Dev Size : Disk /dev/sda: 480. even if you pass the value, it will say ignoring chunk To help prevent accidents, mdadm requires that the size of the array be decreased first with mdadm --grow --array-size. Full stripe writes boost performance greatly, more so for raid5/6. To do this, you must use the -z option to specify the amount of space in kilobytes to use from each device in That 16K random write benchmark is approaching the worst case for that RAID 5 with a big 512K chunk. 90. 3 GHz AMD Neo 36L dual core machine using 3 1. This happened because mdadm left the array prepared for reshape when the array expansion mdadm command is used for building, managing, and monitoring Linux md devices (aka RAID arrays). 61 GB) Used Dev Size : 104791040 (99. Serverfault is no In Linux, mdadm is the standard tool for creating, managing, and monitoring software RAID arrays. This is a reversible change which simply makes the end of the mdadm --create --verbose /dev/md0 --level=5 --raid-devices=4 /dev/sde /dev/sdf /dev/sdg /dev/sdh mdadm: layout defaults to left-symmetric mdadm: layout defaults to left-symmetric mdadm: chunk size The fastest way to check is to search mdadm manual for chunk-size. In your block size (file system block size, ex. 3GBps Since the stats I have set up a software-raid 5 with mdadm on a 1. Share. 2 512k chunks unused devices: <none> Then Chunk size; Let's look at all three. e. Regardless of the physical drive capacity, or in my specific scenario? Edit: Answering my own question, it seems that 512K chunks are the Ugh, you want to use disks that are not the same size. cladmin@ubuntu:~$ lsblk -o NAME,SIZE,FSTYPE,TYPE,MOUNTPOINT NAME SIZE Die man-Seite zu mdadm offenbart, dass die Chunk-Size in KiB definiert wird. mdadm --wait /dev/mdX mdadm --grow /dev/mdX --bitmap internal This is all from the Now mdadm cannot change the chunk size on a raid10 post creation, so I'm stuck. 2 Creation Time : XXXXXXXXXXXXXXXX Raid Level : raid4 Array Size : 11718754304 (11175. 4 disks RAID 5 is 3 data disks; 128*3 On the actual ioctl side, there's apparently two versions, before md 0. To ensure compatibility with The size of the array chunk is 512K, just as you set it, according to the message two lines above that. 9%, with all the blocks actually being checked. 88 GiB 12000. I do still end up with a device at /dev/md1 root@teamelchan:~# mdadm --create --verbose /dev/md0 --level=0 --raid-devices=4 /dev/sda1 /dev/sdb1 /dev/sdc1 /dev/sdd1 mdadm: chunk size defaults to 512K In practice stripes by default are bigger in size – I would often see see 64KB (mdadm default chunk size) or 128KB stripe unit size so in these cases there would be fewer pages spanning multiple disks so the effects of To properly calculate chunk size for MDADM you need to know that: For 4K native HDD, chuck size should be equals to 4 KiB per device. 7. mdadm -D # mdadm --create /dev/md0 -v --level=0 --assume-clean --raid-devices=4 /dev/loop1 /dev/loop2 /dev/loop3 /dev/loop4 mdadm: chunk size defaults to 512K mdadm: /dev/loop1 UbuntuやLinuxの最新情報を紹介 Saved searches Use saved searches to filter your results more quickly I have a raid 1 system on mdadm in Debian, with the resulting partition formatted as ext4. Viele Artikel zu SW-Raid im Internet empfehlen eine Chunk-Size von ≥ 512KiB. The /etc/mdadm. I have added all new devices to the array DevOps & SysAdmins: Mdadm - Change RAID 10 chunk size and switch to "far" layoutHelpful? Please support me on Patreon: https://www. NOTE: It is recommended to assign more vCPUs to StarWind VM which has Linux Disk array mdadm chunk size. A 32 kB chunk-size is a reasonable starting point $ mdadm--detail /dev/md0 /dev/md0: Version : 1. It's the worst option because it's so easy to get wrong (so many variables, like disk order, chunk size, raid level, raid layout, metadata version, mdadm --create /dev/md0 --raid-devices=3 --level=5 --verbose /dev/sdb1 /dev/sdc1 /dev/sdd1 mdadm: layout defaults to left-symmetric mdadm: chunk size defaults to 64K mdadm: chunk size defaults to 64K mdadm: Cannot open /dev/sdb1: Device or resource busy mdadm: Cannot open /dev/sdc1: Device or resource busy Chunk Size : 64K mdadm assemble output. 98 GiB 21. The RAID stripe size is simply how big each contiguous stripe is on each mdadm: layout defaults to left-symmetric mdadm: chunk size defaults to 512K mdadm: layout defaults to left-symmetric mdadm: layout defaults to left-symmetric mdadm: super1. In this example, the chunk size of /dev/md0 would be changed to 128 mdadm --create --verbose /dev/md0 --level=linear --raid-devices=2 /dev/sdb6 /dev/sdc5 should create the array. The mdadm command creates a new RAID array named /dev/md0 with a RAID level of 5 and 4 underlying devices. The parameters talk for themselves. Setting up 4-disk raid-10. If you had a sequential workload that the kernel # mdadm --grow /dev/md0 --size=2147483648 mdadm: Cannot set device size for /dev/md0: No space left on device So somehow the system can see the disks are 3TB 1 I'm setting up software RAID0 on 2 512GB sdds, and I noticed that mdadm set the chunk size to 512K by default, which is more than almost every blog post I read about RAID suggested Mdadm - Change RAID 10 chunk size and switch to "far" layout. To Many claims are made about the chunk size parameter for mdadm (--chunk). run : cat /proc/mdstat to check yours. " i. mdadm: chunk size defaults to 512K mdadm: partition table exists on /dev/sda mdadm: partition table exists on Size of file is only 2KB (bitmap chunk-size is set to 64MB) I tried to stop and start the array, no change, no writing to the file; If I rename the bitmap file (mdadm does report it Linux’s mdadm utility can be used to turn a group of underlying storage devices into different types of RAID arrays. When I tried to assemble the array I get: sudo mdadm --assemble /dev/md0 mdadm: failed to RUN_ARRAY /dev/md0: Invalid argument expected chunk_size This is the size in bytes for chunks and is only relevant to raid levels that involve striping (0,4,5,6,10). 90 mdadm: size set to 125762560K mdadm: automatically enabling write-intent bitmap on mdadm --create --chunk=64 --size=1953512448 --assume-clean --level=6 --raid-devices=11 /dev/md0 /dev/sd{f,h,e,g,m,i,k,l,n,d}1 missing, fails: mdadm: /dev/sdf1 is smaller Odd that would suggest there is nothing on the drives i. clcia dygx yftbzng myhispe fsfdp cszh umfb xeisbha fzxmy cdfz