Re: RAID stripe size question

Hi, Mikael,

Mikael Carneholm wrote:
> An 0+1 array of 4 disks *could* be enough, but I'm still unsure how WAL
> activity correlates to "normal data" activity (is it 1:1, 1:2, 1:4,
> ...?)

I think the main difference is that the WAL activity is mostly linear,
where the normal data activity is rather random access. Thus, a mirror
of few disks (or, with good controller hardware, raid6 on 4 disks or so)
for WAL should be enough to cope with a large set of data and index
disks, who have a lot more time spent in seeking.

Btw, it may make sense to spread different tables or tables and indices
onto different Raid-Sets, as you seem to have enough spindles.

And look into the commit_delay/commit_siblings settings, they allow you
to deal latency for throughput (means a little more latency per
transaction, but much more transactions per second throughput for the
whole system.)

HTH,
Markus

--
Markus Schaber | Logical Tracking&Tracing International AG
Dipl. Inf. | Software Development GIS

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