I am trying to (what else?) improve the performance of the filers that I have. Here are the configs and the environment in which they run. My specific questions follow:
I have two F740's with 14x 18GB FC-AL disks and a trunked 4x 100 Mb/s ethernet card. These filers serve software development sandboxes with a few million files (median file size about 4 kB), not more than a few thousand in the largest directories. These filers are used for both CIFS and NFS client builds; NFS traffic is limited to UDP only (`options nfs.tcp.enable off`) to keep the network overhead down on that protocol. Mix is about 60-75% NFS; the rest, CIFS. Running ONTAP 5.3.4R3P2. CPU load is more often than not above 50%, often 75-90% or more; usually 3,000 - 5,000 ops/; cache age is rarely above 3--most often 1 or 0. Consistency points are usually at the maximum of once every 10 seconds (as measured by disk writes with `sysstat`).
I was poking around on the SPEC pages, and in the footnotes to the NetApp entries are these parameters:
options nosnap 1 # to disable periodic snapshot creation, for reproducibility
options nosnapdir 1 # to avoid inserting .snapshot entry when reading directories
options raid.scrub.enable off # to disable periodic RAID scrubs, for reproducibility
options minra 1 # to minimize file read-ahead
options udp_lg_dgram.xmit_cksum.offload 1 # to offload checksum computations onto the Gigabit NIC
Openboot settings on the F740: setenv java? false # to disable the Java Virtual Machine
http://www.spec.org/osg/sfs97/results/res98q3/sfs97-980805-00008.html http://www.spec.org/osg/sfs97/results/res99q2/sfs97-19990416-00045.html
I have a few questions:
1a. Regarding snapshots, many of my development sandboxes are "disposable" so I don't care about snapshots. The first two options might help me. In addition, if I set `snap reserve volX 0`, will that actually turn off snapshots, and reduce overhead on the filer? The options only seem to turn off *automatic* snapshots and the *display* of the ".snapshot" directory.
1b. Would disabling these two options *prevent* me from `cd`ing into the .snapshot directory? Even though it is visible by default at the root of the mount point, you can `cd` into the directory ".snapshot" at any point:
37 machine:/devel/scratch>ls -a . .. .snapshot toddc 38 machine:/devel/scratch>cd toddc 39 machine:/devel/scratch/toddc>ls -a . Testing.doc devtools .. dump.image.gz 40 machine:/devel/scratch/toddc>cd .snapshot 41 machine:/devel/scratch/toddc/.snapshot>pwd /devel/scratch/toddc/.snapshot 42 machine:/devel/scratch/toddc/.snapshot>ls backup hourly.1 nightly.0 hourly.0 hourly.2
1c. In addition, I'm thinking of breaking up my 14-disk filer from a RAID 13d+1p configuration into, say, two RAID groups and two volumes as 3d+1p and 9d+1p. (Multiple RAID groups are allowed per volume; I assume multiple volumes per RAID group is still disallowed?) The former would have the stuff I need snapshotted and the latter the stuff I don't. I have a churn rate of about 30-40%. Thoughts?
2. What does "options minra 1" buy me? What is the number when minra=off, the default? (If it's just a boolean, nevermind!) Given I have a development environment with lots of small files, it seems as if turning this option on will benefit me a lot. However, some more information on this would help.
3. Does the udp_lg_dgram.xmit_cksum.offload option also apply to quad-ethernet cards? Will it help if the ports are trunked with a virtual interface?
4. Why is my filer running Java? If I disable that, would we see any administration impact? (These filers are administered solely via the CLI.) I do see the messages file logs
[Java Thread]: TimeDaemon: timed: adjusting time
messages all the time. Would I loose the ability to keep the filer in time sync? What else might I loose?
To prevent a knee-jerk reaction, for the purposes of this discussion, upgrading my filer to an F760 is not an option. ;) I want to leverage what I have now, as best I can.
I thought about opening a tech support call, and still may, but I thought some real life input from the trenches would be useful as a start.
Until next time...
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