HI
Just want to add 2 things
+1 to have more than 1 copy of Metadata
The full stride write is important as repetitively been stated here. However there are implementations that have successfully reduced this (IBM FlashCore comes to mind). On the last London UG I presented different storage
On Wed, 2018-09-05 at 13:37 -0400, Frederick Stock wrote:
> Another option for saving space is to not keep 2 copies of the
> metadata within GPFS. The SSDs are mirrored so you have two copies
> though very likely they share a possible single point of failure and
> that could be a deal breaker. I
Hi Kevin,
as you already pointed out, having a RAID stripe size (or a multiple of it) not
matching GPFS blocksize, is a bad idea. Every write would cause a
read-modify-write operation to keep the parity.
So for data LUNs RAID5 with 4+P or 8+P is fully ok.
For metadata, if you are keen on
Hi All,
Wow - my query got more responses than I expected and my sincere thanks to all
who took the time to respond!
At this point in time we do have two GPFS filesystems … one which is basically
“/home” and some software installations and the other which is “/scratch” and
“/data” (former
Perhaps repeating myself, but consider no-RAID or RAID "0" and
-M MaxMetadataReplicas
Specifies the default maximum number of copies of inodes, directories, and
indirect blocks for a file.
Valid values are 1, 2, and 3. This value cannot be less than the value of
DefaultMetadataReplicas. The
A somewhat smarter RAID controller will "only" need to read the old values
of the single changed segment of data and the corresponding parity
segment, and know the new value of the data block. Then it can compute the
new parity segment value.
Not necessarily the entire stripe. Still 2 reads
I have questions about how the GPFS metadata replication of 3 works.
1. Is it basically the same as replication of 2 but just have one more copy,
making recovery much more likely?
1. If there is nothing that is checking that the data was correctly read off
of the device (e.g. CRC
Answers inline based on my recollection of experiences we've had here:
On 9/6/18 12:19 PM, Bryan Banister wrote:
I have questions about how the GPFS metadata replication of 3 works.
1. Is it basically the same as replication of 2 but just have one more
copy, making recovery much more
I thought reads were always round robin's (in some form) unless you set
readreplicapolicy.
And I thought with fsstruct you had to use mmfsck offline to fix.
Simon
From: gpfsug-discuss-boun...@spectrumscale.org
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