Andreas Dilger wrote:
On 20-Oct-09, at 11:32, Doug Hunley wrote:
Is it safe to use tune2fs to alter stride and stripe_width on an ext4
fs once it has been created? Any caveats I should know about? Thanks
The stride is mostly used at fs creation time, but there is no problem
with changing it. The stripe_width is used by the allocator to align
file allocations with the RAID layout.
One question for Eric is whether the new libdisk patches he made will set
the stripe_width to something ridiculous like 512 or 4096 bytes, or if it
just leaves that field unset in that case. I suspect it would be bad for
mballoc to see the stripe_width be such a small value.
well... yes, it does set it to whatever is reported:
+ min_io = blkid_topology_get_minimum_io_size(tp);
+ opt_io = blkid_topology_get_optimal_io_size(tp);
+ blocksize = EXT2_BLOCK_SIZE(fs_param);
+
+ fs_param->s_raid_stride = min_io / blocksize;
+ fs_param->s_raid_stripe_width = opt_io / blocksize;
if mballoc can't handle certain values then maybe the kernel code should
be changed to ignore it? Small values could just as easily come from a
user too ...
-Eric
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