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

[Roy Sigurd Karlsbakk]

An SLC SSD would probably be substansially slower than an array of MLC SSDs, and would be likely to slow down the system for sync writes.

----- Opprinnelig melding -----
> Hi,
> 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
> -
> Extenders.
> 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.
> 
> BR
> 
> Sebastian
> 
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