Hi All,
Sorry if this question is already addressed in the documentation, but I am
still unclear about some details ZIL devices.
I am looking at provisioning some network attached storage with ZFS on the back
end.
In the interests of the 'inexpensive' part of the acronym 'RAID', I am looking
at using SATA drives for the primary storage striped over multiple mirrors.
I will be doing the operating system on a separate set of traditionally
mirrored 15K SAS disks (formatted UFS2).
In the interests of performance given the SATA drives for the main storage, I
am considering provisioning a separate ZIL device, again on 15K SAS.
For the ZIL device, my understanding is that if it fails, everything still
'just works'. Meanwhile, I tend to be a bit paranoid at times and am curious
about having the ZIL device be mirrored.
I suppose with hardware RAID, it would be obvious that I could just mirror two
15K SAS drives that way, export it out as a single device to the operating
system and I am clear.
My question(s) are:
#1. Is it worthwhile to allocate a fast ZIL device to help out with writes to
the sluggish SATA main storage drives? It seems to me that probably this kind
of case might be exactly what ZIL is for?
#2. Is it possible for me to mirror those two 15K SAS drives I want to use for
ZIL directly within ZFS? From the documentation, it seems not, and if I want
to go this way, I'll want hardware RAID1.
#3. Does anybody have any field/production information about just using
low-end (but newer generation) SATA SSDs for the ZIL device? My concern here
is obviously about performance degradation over time with SSD, particularly as
an SSD device. (Again, small budget, I can't afford any of the fancy SSD
stuff).
Thanks,
- Mike
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