Tag Info

Hot answers tagged

11

I know this is probably a hypothetical question... But the IT world really doesn't work that way. There are realistic constraints to consider, plus other things that can influence IOPS... 50GB and 100GB disks don't really exist anymore. Think more: 72, 146, 300, 450, 600, 900, 1200GB in enterprise disks and 500, 1000, 2000, 3000, 4000, 6000GB in ...


7

To answer your question directly - all other things being equal = no change whatsoever when GB changes. You don't measure IOPS with GB. You use the seek time and the latency. I could re-write it all here but these examples below do all that already and I would simply be repeating it: http://www.ryanfrantz.com/posts/calculating-disk-iops/ ...


7

One place where there is a direct relationship between disk size and IOPS is in the Amazon AWS Cloud and other "cloudy services". Two types of AWS services (Elastic Block Store and Relational Database Service ) provide higher IOPS for larger disk sizes. Note that this is an artificial restriction placed by Amazon on their services. There is no ...


4

This is correct... kinda. Use lsscsi. The SCSI device nodes correspond to the controller/target/device naming you see in VMware. Extreme example: root@vdp1:~/#: lsscsi [0:0:0:0] disk VMware Virtual disk 1.0 /dev/sda [0:0:1:0] disk VMware Virtual disk 1.0 /dev/sdb [0:0:4:0] disk VMware Virtual disk 1.0 /dev/sdj ...


4

I should point out that IOPS are not a great measurement of speed on sequential writes, but lets just go with it. I suspect the seek and write times of disk heads is pretty consistent despite the size of the disks. 20 years ago we we're all using 60GB disks with (roughly - certainly not linearly) the same read/write speeds. I am making an educated guess ...


3

The performance added to the storage scales with each spindle added. The rotational speed of the drive is the biggest factor, so adding a 10k RPM drive will give more performance (in terms of IO/s in random IO or MB/s in streaming IO) than a 7.2k RPM drive. The size of the drive has virtually no effect. People say small drives go faster simply because you ...


3

6 Gbs is the speed of the SAS link, not the IO profile of a single disk. Typically the speed in a SAS backplane will be negotiated down to the lowest common denominator so you'll find slow disks that still support high-speed SAS links to allow you to mix disks in a single (external) enclosure or backplane, or to benefit from parallelised IO spread out ...


2

hdparm -T will essentially test the performance of reading disk caching, which is CPU and memory. This tests what read speeds you would get when files are cached in memory (see the cache section for the free command). The nearline SAS drives aren't full SAS drives. They have the same benefits as SAS drives as they use the SAS interface, but are still ...


2

There are several options, depending on what resources you have available: If you have the OS install DVD, you can boot from that (insert the DVD, then either hold the "C" key at startup, or hold Option key and select the DVD in the startup manager). There's a "Utilities" menu in the installer that'll let you run Disk Utility, which can either create a ...


1

Even though tuning kernel parameters stopped the problem, it's actually possible your performance issues were the result of a bug on the Adaptec 5405Z controller that was fixed in a Feb 1, 2012 firmware update. The release notes say "Fixed an issue where the firmware could hang during high I/O stress." Perhaps spreading out the I/O as you did was enough to ...


1

If you assume all else is equal, performance characteristics of disks of larger capacity don't change very much. An 10K RPM FC drive has very similar characteristics regardless of whether it's 300GB or 3TB. The platters rotate at the same rate, and the heads seek at the same speed. Sustained throughput likewise - not much difference. This is the root of a ...



Only top voted, non community-wiki answers of a minimum length are eligible