nice :) well today it use hdd with sata, 500GB with raid 1 (2 disks) the only problem is the disk being old, i must replace it i'm considering ssd only by the price and myth, hdd works well today i have some doubts about performace without the raid card as you told, the last ssd i used was enterprise level not desktop/non enterprise level, and with a raid card well, others experiences and comments are wellcome :) comments about cache (bcache,flashcache,dm cache) are wellcome too 2014-09-30 12:46 GMT-03:00 Andrei Banu <andrei.banu@xxxxxxxxxx>: > Hi, > > I am in no way of the same technical caliber as many of the people on this > list so please take my advice with a grain of salt. However I do have some > experience with Samsung SSDs in RAID 1 software (md-raid) and I would like > to warn you against it. > > My setup is with 840 PROs of 512GB. I did leave free space (not partitioned) > for OP. The SSDs are connected on SATA3. > > I'll give you the result of 2 tests and if you are happy, go ahead: > > READ > root [~]# hdparm -t /dev/sda > /dev/sda: > Timing buffered disk reads: 292 MB in 3.01 seconds = 96.92 MB/sec > > WRITE > root [~]# dd if=/dev/zero of=testn bs=4k count=256k conv=fdatasync > 262144+0 records in > 262144+0 records out > 1073741824 bytes (1.1 GB) copied, 13.4047 s, 80.1 MB/s > > When the setup is fresh you'll get significantly more out of it but after a > while > (this setup is roughly 1 year old) this is what you get with Samsung SSDs in > RAID1 SW. At least this is my experience and I did try to improve it. As a > matter > of fact, before making a secure erase of one of the SSDs the write speed was > under 10MB/s. What you see above is a lot better than what it started out > (but it's true that after the secure erase the read/write speeds were a lot > better but it dropped in a very short time frame). > > A few points: > 1. CAUTION: 840 EVO are proved to have a read speed degradation for old > data written to the drive (this is unrelated to RAID but it probably affects > performance in RAID). > 2. I believe that any SSDs, regardless of the brand, in a software RAID-1 > setup > might be a bad idea. > 3. I believe that the same SSDs in a hardware RAID setup might lead to a > different story. > > Again: I am not a technical wiz (like many of the people on this list) but I > did > have some experience with this so I thought I should let you know. > > Kind regards! > > > > > On 30.09.2014 17:50, Roberto Spadim wrote: >> >> hi guys! >> i will use a ssd raid1, i want know if raid1 trim is supported at mdadm >> i will use a 840 evo (or evo pro not selected the right one yet) 500gb >> each, raid1, today database size is 100gb, i think it will grow >> 10gb/year, i had many space... >> >> the point are: madm raid1 trim is supported? or should i use lvm? >> should i partition it with 400gb and leave 100gb untouched? or should >> i use a hdd+ssd and dmcache? >> >> >> :) thanks guys, that's a small enterprise solution, they can't buy >> raid cards and sas harddisk are same price of ssd :) >> >> any idea/experience and information is wellcome >> >> > -- Roberto Spadim SPAEmpresarial Eng. Automação e Controle -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
