[gpfsug-discuss] RAID config for SSD's used for data

[Simon Thompson (IT Research Support)]

By having many LUNs, you get many IO queues for Linux to play with. Also the raid6 overhead can be quite significant, so it might be better to go with raid1 anyway depending on the controller...

And if only gpfs had some sort of auto tier back up the pools for hot or data caching :-)

Simon
________________________________________
From: gpfsug-discuss-bounces at spectrumscale.org [gpfsug-discuss-bounces at spectrumscale.org] on behalf of Buterbaugh, Kevin L [Kevin.Buterbaugh at Vanderbilt.Edu]
Sent: 19 April 2017 20:53
To: gpfsug main discussion list
Subject: [gpfsug-discuss] RAID config for SSD's used for data

Hi All,

We currently have what I believe is a fairly typical setup … metadata for our GPFS filesystems is the only thing in the system pool and it’s on SSD, while data is on spinning disk (RAID 6 LUNs).  Everything connected via 8 Gb FC SAN.  8 NSD servers.  Roughly 1 PB usable space.

Now lets just say that you have a little bit of money to spend.  Your I/O demands aren’t great - in fact, they’re way on the low end … typical (cumulative) usage is 200 - 600 MB/sec read, less than that for writes.  But while GPFS has always been great and therefore you don’t need to Make GPFS Great Again, you do want to provide your users with the best possible environment.

So you’re considering the purchase of a dual-controller FC storage array with 12 or so 1.8 TB SSD’s in it, with the idea being that that storage would be in its’ own storage pool and that pool would be the default location for I/O for your main filesystem … at least for smaller files.  You intend to use mmapplypolicy nightly to move data to / from this pool and the spinning disk pools.

Given all that … would you configure those disks as 6 RAID 1 mirrors and have 6 different primary NSD servers or would it be feasible to configure one big RAID 6 LUN?  I’m thinking the latter is not a good idea as there could only be one primary NSD server for that one LUN, but given that:  1) I have no experience with this, and 2) I have been wrong once or twice before (<grin>), I’m looking for advice.  Thanks!

—
Kevin Buterbaugh - Senior System Administrator
Vanderbilt University - Advanced Computing Center for Research and Education
Kevin.Buterbaugh at vanderbilt.edu<mailto:Kevin.Buterbaugh at vanderbilt.edu> - (615)875-9633