On 04/01/99 00:34:34 you wrote:
Hi Brian,
64MB file on an F740 running 5.1.2, minra=on on that RAID volume.The filesystem is mounted via NFSv3 and UDP transport. Network connection is fast Ethernet via crossover cable.
What are results with minra=off? Wouldn't that be a better setting for large sequential files?
That was my first reaction as well.
First run is from a Sun E450 reading in the file with dd and 32Kblock size. Second run is from another E450 (same network config, different NIC on the F740) reading in the same file. Reading a file from disk seems to be exceptionally slow.
I agree, this seems slow. How many disks in that volume/raid group in question? Could that file somehow be very fragmented?
And this was my second. Try creating the file "fresh" (via copy) and then reading it (later, after you're sure it's no longer in cache) and seeing the results. Also, I suspect having fewer than 7 drives could be a limiting factor.
Reading the same file from cache is faster, but still not close to what I'd expect over an otherwise quiet 100 Mbps link.
Can't agree with you here. You're getting roughly 8.4 MB/s over link capable of about 10-12.5 MB/s max. Not optimal, but not bad either...
And this was my third. The in-cache response doesn't seem to be out of line given other possible variables.
Bruce
On Thu, 1 Apr 1999 sirbruce@ix.netcom.com wrote:
What are results with minra=off? Wouldn't that be a better setting for large sequential files?
That was my first reaction as well.
What sort of guidelines do people follow when deciding on the minra setting? At one end of the spectrum, you have broadcast video streaming servers that deal exclusively with long, sequential reads. At the other end, you have something like an INN server storing articles in individual files. Are there any tools to help decide which setting is best, or do you just "eyeball" it and try both settings and see which one seems better?
Also, I suspect having fewer than 7 drives could be a limiting factor.
A single drive should be able to sustain 8MB/sec or higher just on its own... a stripe of five drives should hit at least 40MB/sec. sysstat on that filer does in fact report 38 to 43MB/sec disk reads during a "vol scrub".
What sort of guidelines do people follow when deciding on theminra setting? At one end of the spectrum, you have broadcast video streaming servers that deal exclusively with long, sequential reads. At the other end, you have something like an INN server storing articles in individual files. Are there any tools to help decide which setting is best, or do you just "eyeball" it and try both settings and see which one seems better?
My simple rule is minra=on for crazy apps like INN what have tons of small totally random I/O's and minra=off for almost anything else. Basically, if you think caching will help you in any way you want minra off.
A single drive should be able to sustain 8MB/sec or higher just onits own... a stripe of five drives should hit at least 40MB/sec. sysstat on that filer does in fact report 38 to 43MB/sec disk reads during a "vol scrub".
Actually, the 9GB SCSI drives I believe you're using are only rated for a max (not sustained) external transfer rate of 5MB/sec, so the numbers you're seeing really make sense to me. FYI, the max external transfer (not sustained) rate for our 18GB FC-AL drives is a much nicer 12.5MB/sec so you would probably see better (although not necessarily double <g>) sequential performance with those....
-Val. ============================================== Val Bercovici Office: (613)724-8674 Systems Engineer Pager: (800)566-1751 Network Appliance valb@netapp.com Ottawa, Canada FAST,SIMPLE,RELIABLE ==============================================
On Thu, 1 Apr 1999, Val Bercovici (NetApp) wrote:
My simple rule is minra=on for crazy apps like INN what have tons of small totally random I/O's and minra=off for almost anything else. Basically, if you think caching will help you in any way you want minra off.
Ah, okay, so the crossover point is much closer to the "millions of tiny files" end of the spectrum. We have a bunch of F230's with "split" mailbox spools (about 3.5 million inodes) which are still probably better off with minra=on, although another pair with traditional monolithic mailboxes ought to have minra turned off then.
Actually, the 9GB SCSI drives I believe you're using are only rated for a max (not sustained) external transfer rate of 5MB/sec, so the numbers you're seeing really make sense to me.
Only 5MB/sec? That doesn't sound right to me, especially for a 7200-rpm FC-AL drive (the ST19171FC's). The narrow SCSI Quantum in my workstation gets 8.1MB/sec on sequential block reads averaged across the entire drive.
-
Brian Tao -
sirbruce＠ix.netcom.com -
Val Bercovici (NetApp)