Date: Thu, 2 Oct 2014 15:37:49 -0700 From: javocado <javocado@gmail.com> To: FreeBSD Filesystems <freebsd-fs@freebsd.org> Subject: Mirrored SSDs for ZIL/SLOG - safety, flushing, capacitors Message-ID: <CAP1HOmRYy8cX9k7rs4UEzx41Og4phX5U_2OpiUCKBDSRdMf_bQ@mail.gmail.com>
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I'm setting up a SLOG to improve performance on my ZFS-based fileserver. I plan to use 2 mirrored SSD's to create the log device. Before I continue, I have some specific questions how to approach which hardware to use. Primarily, I'm concerned with what damage/corruption may occur when there's a power loss. 1. if some data is not successfully written to the SSD-SLOG device as a result of a power loss, is this a huge deal? Or is it just a loss of some non-fatal meta data? to help avoid any loss: 2. should I only use SSDs with capacitors? does anyone recommend any? I'm seeing good things about the Intel s3500 3. if only one of the SSDs has a capacitor (I plan to use 2 different SSDs to avoid simultaneous/similar failure rates) what might that do to the SLOG mirror after a power loss? Will it know which SSD had the capacitor and thus slightly-newer data to remirror from? 4. flushing: does anyone know if (and which) SSDs are respecting and flushing data to media when told? Thanks!
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