3 ноября 2016 г. 21:46:32 CET, Ivan Nudzik <[email protected]> пишет: > Hi, > Just in short, my observation dealing with the same dilemma… 6 > commodity SATA SSDs and: > > 1. RAIDZ2 on SATA controller, forced 4k sectors (ashift 12) -> speed at > max ~750MB/s > RAID6 on Sun SAS6 LSI, default volume setup by controller BIOS, 32kB > stripe (I think), write cache ON (if battery OK), simple zpool -> speed > at max. ~1GB/s > RAIDZ2 on 6 volumes on Sun SAS6, each volume RAID0 with one disk, > 32kB stripe, write cache ON -> speed at max. ~2.3GB/s > > All 3 cases on the same X4170M2 with SmartOS and simple zpool scrub and > watching zpool status reported speed - fresh install with some VMs. No > extra science. > Reliability winner is No.1. Even if your server is half burnt, you have > quite good change to read your data, in worst case with 6 SATA->USB > caddies and 6 port USB hub. > Speed winner is No.3, but you have to live with understanding, that if > your controller is gone, so almost for sure your data are gone too. > This would be no issue in cloud business… there one physical server > have almost no meaning, when you properly spread services. > Write cache ON if backup battery is healthy, such setting usually would > be there. Disk cache OFF. As far as I remember HP controllers can be in > full details setup just from some boot CD - cache spliced between write > and read in %. > Btw if you go with classic disks, best to think about some small SSDs > for SLOG. I use PCIe cards with two M.2 ports - SLOG mirror one disk on > each card, L2ARC stripe on rest 2. Thinking of some Sun F20 just for > SSD - they are for ~70€ on ebay. > > Regards… > > I. > > On 3 November 2016 at 12:32:12, Gabriele Bulfon ([email protected]) > wrote: > > Hello, > > I'm considering reusing an HP ProLiant DL380e currently running VMware, > scrathing it and reinstalling XStreamOS/illumos (VMware will be moved > elsewhere). > It features 2 hba controllers: > 1- HP Dynamic Smart Array B120i RAID controller (with 4 disks, I will > use 2 as a mirrored boot) > 2- Smart Array P420 (some TB of disks) > > I want to completely bypass hardware array raid and use jbod or > similar. > I found documents around saying that I can just configure each disk as > a single array in the controller, obtaining the same effect. > > Anyone has suggestions? Any problem I may encounter in this transition? > Should I disable any option on the arrays to disable write caching etc? > > Gabriele > > ---------------------------------------------------------------------------------------- > Sonicle S.r.l. : http://www.sonicle.com > Music: http://www.gabrielebulfon.com > Quantum Mechanics : http://www.cdbaby.com/cd/gabrielebulfon > illumos-discuss | Archives | Modify Your Subscription >
Hi, While your comparison is surely practical (thanks for sharing), it seems to have a few flaws in 'apples to oranges' area. The first test (as SATA) was on a different controller, e.g. the MoBo one? The speed difference could be attributed to chips (expensive and smart vs. cheap and dumber) or PCI lane bandwidth (xN vs xM links, or perhaps a "dedicated" vs. cluttered PCI bus overall). With controller cache in place, you also measure not so much disk/algorithm speeds, but memory-to-memory speeds, effectively topping at your PCI bus speed. This is valid and reallife, but limited at bursts of up to cache size (though half a gig is a good long burst). But you need larger longer heavier loads and average over time to see how the raids compare. Or turn off the cache ;) For the SATA case you can dedicate whole disks to ZFS to enable disk cache, or manage it manually with 'format' on the fly, just to compare closer circumstances. If the SSDs have capacitors to take care of proper poweroff, the disk-caches should be safe to stay on. Does the controller have an IT mode (maybe after reflashing)? The most apple-to-apple'ish test would be comparing a raidz2 over jbod (not raid0's) on the otherwise same connection (maybe even still with cache). And make sure 4k you use is your SSD quanta indeed - some have 8k. Hope this helps, Jim -- Typos courtesy of K-9 Mail on my Samsung Android ------------------------------------------- illumos-discuss Archives: https://www.listbox.com/member/archive/182180/=now RSS Feed: https://www.listbox.com/member/archive/rss/182180/21175430-2e6923be Modify Your Subscription: https://www.listbox.com/member/?member_id=21175430&id_secret=21175430-6a77cda4 Powered by Listbox: http://www.listbox.com
