topic Re: Fastest Disk I/O possible: L2K/L3K internal disks in Disk

Fastest Disk I/O possible: L2K/L3K internal disks

Bill McNAMARA_1 — Wed, 15 May 2002 14:37:16 GMT

What kind of throughput can I expect with the following disks:

disk 3 0/0/1/1.0.0 sdisk CLAIMED DEVICE SEAGATE ST39204LC
/dev/dsk/c1t0d0 /dev/rdsk/c1t0d0
disk 4 0/0/1/1.2.0 sdisk CLAIMED DEVICE SEAGATE ST39204LC
/dev/dsk/c1t2d0 /dev/rdsk/c1t2d0

I need as much as possible speed, (random i/o, read and write) in an L2k/L3k

What is the max possible throughput I can get to the disk based on standard configurations.

What disks can I order/upgrade to in order to maximise the throughput.

What is the best way to measure disk i/o

iostat ?
sar ?

Later,
Bill

Re: Fastest Disk I/O possible: L2K/L3K internal disks

Jeff Schussele — Wed, 15 May 2002 14:59:07 GMT

Hi Bill,

This is a 9Gb 10K rpm drive - giving 25-40 Mb/sec xfer rate, 5.2 avg seek & 2.9 msec latency.

Here's the URL for the specs:

http://www.seagate.com/support/disc/specs/scsi/st39204lc.html

A faster disk would be a 15k rpm such as the ST318453LC - this has 49-75 xfer rate, 3.6 avg seek & 2.0 msec latency

Here's a URL for info

http://www.seagate.com/cda/newsinfo/newsroom/releases/article/0,,1425,00.html

BUT I'm not sure if 15k drives are supported internally in an L-class due to heat. Also note that Seagate's not selling 9Gb 15k disks - 18 is as low as you can go.

For measurement I'd use a large file & copy it off of & into both drives from the same location & time it (timex?)as a rough test.
Proposing & preparing a real-world random I/O test is another thing & a lot more complicated.

Bottom line...if 9Gb is what you want then you've got about as good as you can get....but 15k is faster.

Rgds,
Jeff

Re: Fastest Disk I/O possible: L2K/L3K internal disks

Pete Randall — Wed, 15 May 2002 14:59:26 GMT

Bill,

From what I can find on the seagate site, the ST39204LC
is a 10K rpm drive with an average seek time of 5.2ms. I'm not having any luck finding any comparison charts but I would think you would have to be better off with a 15K rpm drive. Still searching for a model number for you.

Pete

Re: Fastest Disk I/O possible: L2K/L3K internal disks

Pete Randall — Wed, 15 May 2002 15:00:43 GMT

Bill,

I see Jeff already found a model number so I'll give up.

Good luck,
Pete

Re: Fastest Disk I/O possible: L2K/L3K internal disks

Bill Hassell — Wed, 15 May 2002 15:09:42 GMT

No easy way to answer the question because it all depends. The internal disks are fairly fast but compared to what? Random I/O is seldom random but clustered depending on the applications and the opsystem's usage.

If you want the fastest disks, don't use SCSI, use fibre channel and get yourself a disk array where the specialized processing to handle disk striping, caching and mirroring are handled in dedicated hardware. HP's Virtual Arrays are a good choice, but max out the onboard cache and study the config documents once you get the array hooked up.

As far as tools, nothing in HP-UX is going to give really useful data since you have to characterize your application first. Then you have to measure the completion rate in the app and perhaps move the data around to other disks to prevent thrashing.

Re: Fastest Disk I/O possible: L2K/L3K internal disks

Mark Greene_1 — Wed, 15 May 2002 16:01:07 GMT

When we bought our 2 L2k systems last Nov., they each came with 2 18.2gig 10k rpm drives internally. I inquired with HP about getting 15k rmp drives, and was told at that time none were supported for use as internal drives. I do not know if that has changed, or not.

HTH
mark

Re: Fastest Disk I/O possible: L2K/L3K internal disks

Don Capps_1 — Thu, 16 May 2002 11:24:18 GMT

I would recommend using a file I/O benchmark like Iozone to measure the performance. http://www.iozone.org