[OpenIndiana-discuss] Raid type selection for large # of ssds

Sebastian Gabler sequoiamobil at gmx.net
Mon Oct 8 15:01:13 UTC 2012

from what I understood from negative experience with a 12-drive SSD RAID 
set build with MDRaid on linux, and from answers to a related question I 
raised recently in this list, it is not so easy to engineer a 
configuration using a large count of SSDs anyhow. The budget option, 
using SATA SSDs, seems to be critical in some terms. Using an SSD type 
based on a controller using compression seems to be a suboptimal choice  
for any data that will not compress efficiently (which is more likely 
writing as a stripe set (RaidZn)). Other concern seems to be SATA vs SAS 
in general, and compatibility of SATA SSDs with the usual SAS HBAs and - 
One should be aware that any of these aspects is prone to make the vdev 
unresponsible, or even kick drives out of the vdev. Should that be a 
systematic issue, the stripe set will not rebuild properly or even be 
lost in an instant, with no parity level offering protection.

Another option could be to look into a setup that is using a SLC or 
RAM-based ZIL device, and/or a large SSD based L2ARC.  That's what I am 
looking into, currently.



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