summaryrefslogtreecommitdiffstats
path: root/Documentation/md
AgeCommit message (Collapse)AuthorFilesLines
2018-01-15raid5-ppl: PPL support for disks with write-back cache enabledTomasz Majchrzak1-3/+4
In order to provide data consistency with PPL for disks with write-back cache enabled all data has to be flushed to disks before next PPL entry. The disks to be flushed are marked in the bitmap. It's modified under a mutex and it's only read after PPL io unit is submitted. A limitation of 64 disks in the array has been introduced to keep data structures and implementation simple. RAID5 arrays with so many disks are not likely due to high risk of multiple disks failure. Such restriction should not be a real life limitation. With write-back cache disabled next PPL entry is submitted when data write for current one completes. Data flush defers next log submission so trigger it when there are no stripes for handling found. As PPL assures all data is flushed to disk at request completion, just acknowledge flush request when PPL is enabled. Signed-off-by: Tomasz Majchrzak <tomasz.majchrzak@intel.com> Signed-off-by: Shaohua Li <sh.li@alibaba-inc.com>
2017-11-01md-cluster: update document for raid10Guoqing Jiang1-1/+2
Signed-off-by: Guoqing Jiang <gqjiang@suse.com> Signed-off-by: Shaohua Li <shli@fb.com>
2017-05-03Merge branch 'for-linus' of ↵Linus Torvalds2-1/+45
git://git.kernel.org/pub/scm/linux/kernel/git/shli/md Pull MD updates from Shaohua Li: - Add Partial Parity Log (ppl) feature found in Intel IMSM raid array by Artur Paszkiewicz. This feature is another way to close RAID5 writehole. The Linux implementation is also available for normal RAID5 array if specific superblock bit is set. - A number of md-cluser fixes and enabling md-cluster array resize from Guoqing Jiang - A bunch of patches from Ming Lei and Neil Brown to rewrite MD bio handling related code. Now MD doesn't directly access bio bvec, bi_phys_segments and uses modern bio API for bio split. - Improve RAID5 IO pattern to improve performance for hard disk based RAID5/6 from me. - Several patches from Song Liu to speed up raid5-cache recovery and allow raid5 cache feature disabling in runtime. - Fix a performance regression in raid1 resync from Xiao Ni. - Other cleanup and fixes from various people. * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/shli/md: (84 commits) md/raid10: skip spare disk as 'first' disk md/raid1: Use a new variable to count flighting sync requests md: clear WantReplacement once disk is removed md/raid1/10: remove unused queue md: handle read-only member devices better. md/raid10: wait up frozen array in handle_write_completed uapi: fix linux/raid/md_p.h userspace compilation error md-cluster: Fix a memleak in an error handling path md: support disabling of create-on-open semantics. md: allow creation of mdNNN arrays via md_mod/parameters/new_array raid5-ppl: use a single mempool for ppl_io_unit and header_page md/raid0: fix up bio splitting. md/linear: improve bio splitting. md/raid5: make chunk_aligned_read() split bios more cleanly. md/raid10: simplify handle_read_error() md/raid10: simplify the splitting of requests. md/raid1: factor out flush_bio_list() md/raid1: simplify handle_read_error(). Revert "block: introduce bio_copy_data_partial" md/raid1: simplify alloc_behind_master_bio() ...
2017-03-17Documentation: md: md-cluster.txt: Fix typosTamara Diaconita1-1/+1
Fix typos in md-cluster.txt file to make documentation clear. Signed-off-by: Tamara Diaconita <diaconita.tamara@gmail.com> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2017-03-16raid5-ppl: Partial Parity Log write logging implementationArtur Paszkiewicz1-0/+44
Implement the calculation of partial parity for a stripe and PPL write logging functionality. The description of PPL is added to the documentation. More details can be found in the comments in raid5-ppl.c. Attach a page for holding the partial parity data to stripe_head. Allocate it only if mddev has the MD_HAS_PPL flag set. Partial parity is the xor of not modified data chunks of a stripe and is calculated as follows: - reconstruct-write case: xor data from all not updated disks in a stripe - read-modify-write case: xor old data and parity from all updated disks in a stripe Implement it using the async_tx API and integrate into raid_run_ops(). It must be called when we still have access to old data, so do it when STRIPE_OP_BIODRAIN is set, but before ops_run_prexor5(). The result is stored into sh->ppl_page. Partial parity is not meaningful for full stripe write and is not stored in the log or used for recovery, so don't attempt to calculate it when stripe has STRIPE_FULL_WRITE. Put the PPL metadata structures to md_p.h because userspace tools (mdadm) will also need to read/write PPL. Warn about using PPL with enabled disk volatile write-back cache for now. It can be removed once disk cache flushing before writing PPL is implemented. Signed-off-by: Artur Paszkiewicz <artur.paszkiewicz@intel.com> Signed-off-by: Shaohua Li <shli@fb.com>
2017-03-16md-cluster: add the support for resizeGuoqing Jiang1-1/+1
To update size for cluster raid, we need to make sure all nodes can perform the change successfully. However, it is possible that some of them can't do it due to failure (bitmap_resize could fail). So we need to consider the issue before we set the capacity unconditionally, and we use below steps to perform sanity check. 1. A change the size, then broadcast METADATA_UPDATED msg. 2. B and C receive METADATA_UPDATED change the size excepts call set_capacity, sync_size is not update if the change failed. Also call bitmap_update_sb to sync sb to disk. 3. A checks other node's sync_size, if sync_size has been updated in all nodes, then send CHANGE_CAPACITY msg otherwise send msg to revert previous change. 4. B and C call set_capacity if receive CHANGE_CAPACITY msg, otherwise pers->resize will be called to restore the old value. Reviewed-by: NeilBrown <neilb@suse.com> Signed-off-by: Guoqing Jiang <gqjiang@suse.com> Signed-off-by: Shaohua Li <shli@fb.com>
2017-02-13MD: add doc for raid5-cacheShaohua Li1-0/+109
I'm starting document of the raid5-cache feature. Please note this is a kernel doc instead of a mdadm manual, so I don't add the details about how to use the feature in mdadm side. Cc: NeilBrown <neilb@suse.com> Reviewed-by: Song Liu <songliubraving@fb.com> Signed-off-by: Shaohua Li <shli@fb.com>
2017-02-13Documentation: move MD related doc into a separate dirShaohua Li1-0/+324
Signed-off-by: Shaohua Li <shli@fb.com>