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Require number of stripes to be greater than parity devices in higher RAID.

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Also, add some comments to code that I recently added that may be unclear
otherwise.
This commit is contained in:
Jonathan Earl Brassow 2012-02-23 17:36:35 +00:00
parent d4836062ff
commit 870762d8e3
4 changed files with 30 additions and 3 deletions
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1
WHATS_NEW
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@ -1,5 +1,6 @@
Version 2.02.93 -
====================================
Require number of stripes to be greater than parity devices in higher RAID.
Add LVMetaD systemd units.
Fix allocation code to allow replacement of single RAID 4/5/6 device.
Check all tags and LV names are in a valid form in vg_validate.

16
lib/metadata/lv_manip.c
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@ -752,6 +752,22 @@ static struct alloc_handle *_alloc_init(struct cmd_context *cmd,
area_count = stripes;
size = sizeof(*ah);
/*
* It is a requirement that RAID 4/5/6 are created with a number of
* stripes that is greater than the number of parity devices. (e.g
* RAID4/5 must have at least 2 stripes and RAID6 must have at least
* 3.) It is also a constraint that, when replacing individual devices
* in a RAID 4/5/6 array, no more devices can be replaced than
* there are parity devices. (Otherwise, there would not be enough
* redundancy to maintain the array.) Understanding these two
* constraints allows us to infer whether the caller of this function
* is intending to allocate an entire array or just replacement
* component devices. In the former case, we must account for the
* necessary parity_count. In the later case, we do not need to
* account for the extra parity devices because the array already
* exists and they only want replacement drives.
*/
parity_count = (area_count <= segtype->parity_devs) ? 0 :
segtype->parity_devs;
alloc_count = area_count + parity_count;

9
lib/metadata/raid_manip.c
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@ -519,9 +519,18 @@ static int _alloc_image_components(struct logical_volume *lv,
else if (!(segtype = get_segtype_from_string(lv->vg->cmd, "raid1")))
return_0;
/*
* The number of extents is based on the RAID type. For RAID1,
* each of the rimages is the same size - 'le_count'. However
* for RAID 4/5/6, the stripes add together (NOT including the parity
* devices) to equal 'le_count'. Thus, when we are allocating
* individual devies, we must specify how large the individual device
* is along with the number we want ('count').
*/
extents = (segtype->parity_devs) ?
(lv->le_count / (seg->area_count - segtype->parity_devs)) :
lv->le_count;
if (!(ah = allocate_extents(lv->vg, NULL, segtype, 0, count, count,
region_size, extents, pvs,
lv->alloc, parallel_areas)))

7
tools/lvcreate.c
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@ -485,9 +485,10 @@ static int _read_raid_params(struct lvcreate_params *lp,
*
* For RAID 4/5/6, these values must be set.
*/
if (!segtype_is_mirrored(lp->segtype) && (lp->stripes < 2)) {
log_error("Number of stripes to %s not specified",
lp->segtype->name);
if (!segtype_is_mirrored(lp->segtype) &&
(lp->stripes <= lp->segtype->parity_devs)) {
log_error("Number of stripes must be at least %d for %s",
lp->segtype->parity_devs + 1, lp->segtype->name);
return 0;
}