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what's a good IO Speed for 4x1TB RAID10
AlexanderM
Member, Top Host, Host Rep
in Help
Hey,
So i got a new dedi with 4x1TB In SW RAID10, as the drives are cheap ($15/month/each) I will assume they have been previously used. I have also installed cPanel (No accounts)
avg-cpu: %user %nice %system %iowait %steal %idle
0.28 0.37 0.27 0.23 0.00 98.85
dd if=/dev/zero of=test bs=64k count=16k conv=fdatasync; unlink test
16384+0 records in
16384+0 records out
1073741824 bytes (1.1 GB) copied, 6.19182 s, 173 MB/s
dd if=/dev/zero of=test bs=64k count=16k conv=fdatasync; unlink test
16384+0 records in
16384+0 records out
1073741824 bytes (1.1 GB) copied, 6.36646 s, 169 MB/s
dd if=/dev/zero of=test bs=64k count=16k conv=fdatasync; unlink test
16384+0 records in
16384+0 records out
1073741824 bytes (1.1 GB) copied, 6.15193 s, 175 MB/s
I think 170MB/s with SW Raid10 is good, but confused to why there is 0.23% IO Wait. What do you think?
Cheers
Comments
Seems reasonable for software. Are these SATA 2 or SATA 3 drives?
Not sure, for $15 i would guess SATA2
Seems about right, generally you will get around 100mb/s from a single drive and with 2 I usually see it around 170 - 195 mb/s
Just remember that with cPanel installed it draws a decent amount of resource just sitting idle with no accounts.
hdparm and/or smartctl would give you more info on your drives - SATA revision, power-on hours, etc. Your speeds look good though - approaching 200MB/sec for 4x drives in SW RAID10 is very respectable.
SATA2 vs SATA3 isn't going to matter much for 1 TB hard drives. A 1 TB hard drive is not going to be able to saturate SATA2.
Just to let you know, I ended up getting HW raid w/ bbu and getting about 300MB/s now.
@alexander which HW raid controller?
I have 4x3tb in raid 10 , I get 340mbps
Do people use SW RAID 10? I always thought RAID1 or 0 were the only things worth doing with SW RAID. I would imagine RAID10 would add a lot of load to the CPU doing it in SW.
Well raid10 is raid 1+0. It shouldn't cause a lot of CPU load.
Does your raid card have cache on it? If so, are you running in write-back or write-through mode?
Write-back means the card is actively caching writes (and therefore should have a BBU) and write-through means all writes are immediately flushed to disk. It makes a real big difference in performance for smaller files on a non-sequential basis.
1+0 + at least 4 drives as opposed to only 2 and at least 2x the amount of calculations.
but 2 x 0 is still =0.
There's really not much calculation(OK not really 0, but not too significant in today's CPU power.) happening here as the CPU does not do parity calculation unlike with other raids. I'm not saying that using raid cards for raid 10 is a bad idea though.
Now getting about 350MB/s it's a LSI raid card.
When you say software do you mean Motherboard raid or mdadm?
nm, the image did not load I see it was mdadm now
Write-back I'm assuming? Run dd a few times with the conv=fdatasync flag and see if it is consistent.
I've never tried it so I really don't know. I was hoping someone who uses Software RAID10 and 1 would chime in. True that with todays processors it may be no big deal as opposed to just a few years ago. However, there may be a lot of interrupts generated which could slow things down. Also that I/O is on the motherboard in the chipset that also has to do other things as opposed to a raid card where it's isolated from other things.
Again, I don't know the answer and was hoping someone who has done it could chime in.
What model LSI card is it? They offer a lot of products, some are excellent and some are very much entry level. The type matters.
@sman, I'm not sure about software RAID10, but for RAID 1 the processor utilization is generally insignificant under normal usage. However, if there's a rebuild/resync going on, the overall load will definitely shoot up.
I use software RAID 1 all the time. The thing I like most about it is that configuration is the same regardless of hardware. With HW raid you have to learn proprietary configuration. Most everyone uses LSI now a days so that's not such a big deal but before I was using 3ware before LSI bought them so it created more complications having to know different configurations. That is the last thing you want to deal with when the proverbial stuff hits the fan.
Good point about rebuilds. With RAID1 it's very significant. That is the biggest disadvantage with sw raid imho.
@jbiloh it's the LSI 9260-4 highest I've got is 420MB/s
Yeah that's a pretty good card, it's cached with 512MB onboard.
Now you need to figure out whether you're running in write-back or write-through mode. Install MegaCLi.
I have 4x3tb in raid 10 , I get 360mbps