From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Brown Subject: Re: Home desktop/server RAID upgrade Date: Sun, 01 Jun 2014 17:06:27 +0200 Message-ID: <538B4173.3030202@hesbynett.no> References: <20140530212907.0b00e8a3@netstation> <5389B463.5020100@hesbynett.no> <8mtskybo2j1i4l2bqu51l7ll.1401554092920@email.android.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: Sender: linux-raid-owner@vger.kernel.org To: Mark Knecht , Craig Curtin Cc: "L.M.J" , Linux-RAID List-Id: linux-raid.ids Hi Mark, What would be really useful here is a description of what you actually=20 /want/. What do you want to do with these drives? What sort of files=20 are they - big or small? Do you need fast access for large files? Do=20 you need fast access for many files in parallel? How important is the=20 data? How important is uptime? What sort of backups do you have? Wha= t=20 will the future be like - are you making one big system to last for the= =20 foreseeable future, or do you need something that can easily be=20 expanded? Are you looking for "fun, interesting and modern" or "boring= =20 but well-tested" solutions? Then you need to make a list of the hardware you have, or the budget fo= r=20 new hardware. Without know at least roughly what you are looking for, it's easy to en= d=20 up with expensive SSDs because they are "cool", even though you might=20 get more speed for your money with a couple of slow rust disks and a bi= t=20 more ram in your system. It may be that there is no need for any sort=20 of raid at all - perhaps one big main disk is fine, and the rest of the= =20 money spent on a backup disk (possibly external) with rsync'd copies of= =20 your data. This would mean longer downtime if your main disk failed -=20 but it also gives some protection against user error. And perhaps btrfs with raid1 would be the best choice. A raid10,f2 is often the best choice for desktops or workstations with = 2=20 or 3 hard disks, but it is not necessarily /the/ best choice. mvh., David On 01/06/14 16:25, Mark Knecht wrote: > Hi Craig, > Responding to both you and David Brown. Thanks for your ideas. > > - Mark > > On Sat, May 31, 2014 at 9:40 AM, Craig Curtin = wrote: >> It sounds like the op has additional data ports on his MOBO - wouldn= 't he be >> better off looking at a couple of SSDs in raid 1 for his OS, swap et= c and >> his VMs and then leave the rest for data as raid5 - By moving the th= ings >> from the existing drives he gets back space and only purchases a cou= ple of >> good sized fast SSDs now >> > > It's a possibility. I can get 240GB SSDs in the $120 range so that's > $240 for RAID1. If I take the five existing 500GB drives and > reconfigure for RAID5 that's 2TB. Overall it's not bad going from > 1.4TB to about 2.2TB but being it's not all one big disk I'll likely > never use it all as efficiently. Still, it's an option. > > I do in fact have extra ports: > > c2RAID6 ~ # lspci | grep SATA > 00:1f.2 IDE interface: Intel Corporation 82801JI (ICH10 Family) 4 por= t > SATA IDE Controller #1 > 00:1f.5 IDE interface: Intel Corporation 82801JI (ICH10 Family) 2 por= t > SATA IDE Controller #2 > 03:00.0 SATA controller: Marvell Technology Group Ltd. 88SE9123 PCIe > SATA 6.0 Gb/s controller (rev 11) > 06:00.0 SATA controller: JMicron Technology Corp. JMB363 SATA/IDE > Controller (rev 03) > 06:00.1 IDE interface: JMicron Technology Corp. JMB363 SATA/IDE > Controller (rev 03) > c2RAID6 ~ # > > Currently my 5-drive RAID6 uses 5 of the Intel ports. The 6th port > goes to the CD/DVD drive. Some time ago I bought the SATA3 Marvell > card and a smaller (120GB) SSD. I put Gentoo on it and played around = a > bit but I've never really used it day-to-day. Part of my 2-drive RAID= 1 > thinking was that I could build the new RAID1 on the SATA3 controller > not even touch the existing RAID6. If it works reliably on that > controller I'd be done and have 3TB. > > I think David's RAID10 3-drive solution could possibly work if I buy = 3 > of the lower cost new WD drives. I'll need to think about that. Not > sure. > > Thanks, > Mark > > > On Sat, May 31, 2014 at 9:40 AM, Craig Curtin = wrote: >> It sounds like the op has additional data ports on his MOBO - wouldn= 't he be >> better off looking at a couple of SSDs in raid 1 for his OS, swap et= c and >> his VMs and then leave the rest for data as raid5 - By moving the th= ings >> from the existing drives he gets back space and only purchases a cou= ple of >> good sized fast SSDs now >> >> >> Sent from my Samsung tablet >> >> . >> >> >> -------- Original message -------- >> From: David Brown >> Date:31/05/2014 21:01 (GMT+10:00) >> To: Mark Knecht ,"L.M.J" >> Cc: Linux-RAID >> Subject: Re: Home desktop/server RAID upgrade >> >> On 30/05/14 22:14, Mark Knecht wrote: >>> On Fri, May 30, 2014 at 12:29 PM, L.M.J >>> wrote: >>>> Le Fri, 30 May 2014 12:04:07 -0700, Mark Knecht >>>> a =C3=A9crit : >>>> >>>>> In a RAID1 would a 3-drive Red RAID1 possibly be faster than the >>>>> 2-drive Se RAID1 and at the same time give me more safety? >>>> >>>> Just a question inside the question : how do you manager a RAID1 >>>> with 3 drives ? Maybe you're talking about RAID5 then ? >>> >>> OK, I'm no RAID expert but RAID1 is just drives in parallel right. = 2 >>> drives, 3 drives, 4 drives, all holding exactly the same data. In >>> the case of a 3-drive RAID1 - if there is such a beast - I could >>> safely lose 2 drives. You ask a reasonable question though as maybe >>> the way this is actually done is 2 drives + a hot spare in the box >>> that gets sync'ed if and only if one drive fails. Not sure and mayb= e >>> I'm totally wrong about that. >>> >>> A 3-drive RAID5 would be 2 drives in series - in this case making >>> 6TB - and then the 3rd drive being the redundancy. In the case of a >>> 3-drive RAID5 I could safely lose 1 drive. >>> >>> In my case I don't need more than 3TB, so an option would be a >>> 3-drive RAID5 made out of 2TB drives which would give me 4TB but I >>> don't need the space as much as I want the redundancy and I think >>> RAID5 is slower than RAID1. Additionally some more mdadm RAID >>> knowledgeable people on other lists say Linux mdadm RAID1 would be >>> faster as it will get data from more than one drive at a time. (Or >>> possibly get data from which ever drive returns it the fastest. Not >>> sure.) >>> >>> I believe one good option if I wanted 4 physical drives would be >>> RAID10 but that's getting more complicated again which I didn't >>> really want to do. >>> >>> So maybe it is just 2 drives and the 3 drive version isn't even a >>> possibility? Could be. >> >> With 3 drives, you have several possibilities. >> >> Raid5 makes "stripes" across the three drives, with 2 parts holding = data >> and one part holding parity to provide redundancy. >> >> Raid1 is commonly called "mirroring", because you get the same data = on >> each disk. md raid has no problem making a 3-way mirror, so that ea= ch >> disk is identical. This gives you excellent redundancy, and you can >> make three different reads in parallel - but writes have to go to ea= ch >> disk, which can be a little slower than using 2 disks. It's not oft= en >> that people need that level of redundancy. >> >> Another option with md raid is the raid10 setups. For many uses, th= e >> fastest arrangement is raid10,f2. This means there is two copies of= all >> your data (f3 would be three copies), with a "far" layout. >> >> >> >> With this arrangement, reads are striped across all three disks, whi= ch >> is fast for large reads. Small reads can be handled in parallel. M= ost >> reads while be handled from the outer half of the disk, which is fas= ter >> and needs less head movement - so reading is on average faster than = a >> raid0 on the same disks. Small writes are fast, but large writes >> require quite a bit of head movement to get everything written twice= to >> different parts of the disks. >> >> The "best" option always depends on your needs - how you want to acc= ess >> your files. A layout geared to fast striped reads of large files wi= ll >> be poorer for parallel small writes, and vice versa. raid10,f2 is o= ften >> the best choice for a desktop or small system - but it is not very >> flexible if you later want to add new disks or replace the disks wit= h >> bigger ones. >> >> md raid is flexible enough that it will even let you make a 3 disk r= aid6 >> array if you want - but a 3-way raid1 mirror will give you the same = disk >> space and much better performance. >> -- To unsubscribe from this list: send the line "unsubscribe linux-raid" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html