Quoting Ben Rockwood <[email protected]>:
[email protected] wrote:
I noticed alot of this where the pool members had no activity
according to iostat, but the ssd being used heavily. I don't really
understand, but can someone give me some insight into this?
The SSD doing SLOG (ZIL) is recording all the synchronous writes as they
come in and then returning the "ok" to the calling process. Meanwhile,
the write transactions are queuing up in memory (a "transaction group",
txg) waiting to be flushed to physical disk (a "txg sync") every 30 seconds.
If you watch iostat for a while, you should see almost constant activity
to the SLOG disk and then a big burst of write IO approx every 30
seconds; possibly more frequently depending on how fast your writing
data into memory.
benr.
Thanks very much again.
What happens if the log device for a pool dies suddenly?
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