----- Original Message ----- From: Todd C. Merrill tmerrill@mathworks.com To: toasters@mathworks.com Sent: Tuesday, February 22, 2000 7:56 AM Subject: Re: NVRAM memory
On Fri, 18 Feb 2000, Karl Swartz wrote:
to the cluster partner.) Data and metadata writes are logged to the first chunk until one of two events triggers the establishment of a new consistency point on disk, which consists of writing out all of the logged writes while sending new writes to the other NVRAM chunk.
Is it really both data and metadata that gets written to NVRAM? What gets put into the RAM cache, then, just disk reads? Where to the WAFL logs get written?
Actually, while the RAM is primarily used for cacheing reads and anything else the OS needs, writes are actually logged to both RAM and NVRAM. The NVRAM is just used for stable storage in case of emergency (crash).
I was just examining one of my F740's, which is often running 4-5,000 ops/s with 0 or 1 minute cache ages, but the NVRAM stats don't seem as bad as that dude with the F760:
cp_from_timer = 153482 cp_from_snapshot = 94030 cp_from_low_water = 0 cp_from_high_water = 0 cp_from_log_full = 50913 cp_from_timer_nvlog = 0 cp_from_cp = 347
~20% are "log full" writes, higher than Bruce's rule-of-thumb 10%, but the nasty one people are mentioning "cp_from_cp" is pretty small.
I agree. Also, from your systat, you're going 5 or more seconds between writes, so you aren't really that write-loaded.
Having more options regarding NVRAM and RAM cache configurations in filers would be great, not this current "one-size-fits-all" sh^H^Hstuff.
I think you clearly need more RAM, but if you're already maxed, you basically need to accept that you need another filer. The filers are fairly highly tuned so the CPU is appropriate for the RAM and NVRAM, so it is a relatively rare environment that maxes out one without coming close to maxing out the others.
Bruce